Name: The Monroe Calculator Models K, KA, and L @jaapsch2
Uploaded: 2026-09-17T08:17:00-05:00
Duration: 8 min 17 s
Description: The Monroe Calculator Models K, KA, and L

The Monroe Calculator Models K, KA, and L

Jaap Scherphuis 2026-09-17 | The Monroe Calculator Models K, KA, and L

26-sided antique stone die

Jaap Scherphuis 2022-11-19 | This antique gaming die was made in Zöblitz from the locally mined serpentine stone, probably between 1880 and 1910. It is a rhombicuboctahedron, so it has 26 sides. Only the 18 square sides are used. Twelve sides have the numbers 1 to 12, and six sides have letters. Two games are played simultaneously. The letters are for Put & Take, a game that goes back to the middle ages.

For more information about this die, please visit my website:
jaapsch.net/stuff/zoblitz.htm

0:00 Introduction
0:52 History
1:46 Instructions
8:39 Serpentine
9:37 Carving
10:21 Outro

The AEG KAL portable ticket machine

Jaap Scherphuis 2022-11-04 | This AEG KAL ticket machine was used by the Dutch national railways in the 1970s. The ticket details are set with the input pins, and a turn of the crank then issues a newly printed ticket. It has a locked cartridge with a control copy of all tickets printed.

For more information on this and other machines in my collection, please visit my website:
jaapsch.net/mechcalc

0:00 Introduction
0:23 Input
1:13 Printing a ticket
2:07 Removing from the stand
2:29 Counter registers
3:33 Opening the case
4:05 Control cartridge
6:24 Ink roller
6:53 Setting the date
7:15 Print locking mechanism
8:04 Print cycle
9:20 Outro

The Olivetti Summa 15 adding machine

Jaap Scherphuis 2022-10-22 | The Olivetti Summa 15 adding machine was made in Italy in the 1950s. Its most unusual feature is the multi-function button that looks like a joystick.

For more information on this and other machines in my collection, please visit my website:
jaapsch.net/mechcalc

0:00 Introduction, history
1:06 Manual lever
1:36 Paper feed
1:53 Multi-function button
2:30 Entering numbers, clearing input
2:57 Addition
3:15 Totals and subtotals
4:05 Subtraction
4:25 Non-Add function
4:49 Button release
5:08 Repeat, multiplication
6:28 Ink ribbon
7:05 Negative totals
7:42 Serial number
8:11 Outro

Precisa 102-1 adding machine

Jaap Scherphuis 2022-10-08 | The Precisa 102-1 adding machine was made in Switzerland in the early 1950s. It has some quirks that you need to be aware of when using it, and its recall functionality is very unusual.

For more information on this machine and others in my collection, please visit my website:
jaapsch.net/mechcalc

0:00 Introduction
0:51 Addition
1:16 Totals and subtotals
1:58 Subtraction
2:25 Negative totals
3:30 Non-add
3:55 Non-print
4:29 Repeat, multiplication
5:34 Recall
8:17 Crossbow logo
8:50 Opening the case
10:25 Printing mechanism
11:01 Subtraction mechanism
11:53 Non-print mechanism
12:40 Reassembling case
13:08 Outro

The Addo-X 341 adding machine

Jaap Scherphuis 2022-09-25 | The Addo-X 341 is an adding machine made in Sweden in the 1950s. My version has a carriage for feeding paper sheets, but most just had a simple paper roll.

For more information on this and other machines in my collection, please visit my website:
jaapsch.net/mechcalc

0:00 Introduction
0:25 History
1:35 Entering numbers
2:00 Addition
2:16 Subtraction
2:50 Subtotals and totals
4:20 Symmetric keyboard
4:45 Multiplication
5:55 Step-O-Matic
6:54 Non-Add
7:14 Carriage
8:44 Addo-X 351
9:33 Ink ribbon
9:49 Power cord
11:06 Outro

The Olympia AE-8 adding machine

Jaap Scherphuis 2022-08-30 | The Olympia AE-8 is an adding machine from 1967. It is fairly unremarkable, with a standard keyboard and controls.

For more information about this and other calculators in my collection, please visit my website:
jaapsch.net/mechcalc

0:00 Introduction
0:51 Addition
1:17 Total/Subtotal
2:05 Subtraction
2:39 Negative totals
3:09 Non-add
3:29 Clearing
3:38 Repetition/Multiplication
5:02 Ink ribbon
5:47 Opening case
7:30 Power cord
8:34 Inserting paper
9:26 Mechanism in action
10:59 Outro

The Summira S printing adding machine

Jaap Scherphuis 2022-08-05 | The Summira S is a version of the Summira 7 adding machine but with a printer mechanism at the back. Pulling the large handle will cause the current input to be printed, either in black or in red depending on whether subtraction mode is selected.

For more information about this and other calculating machines in my collection, please visit my website:
jaapsch.net/mechcalc

0:00 Introduction
0:19 Addition
1:02 Clearing
1:32 Multiplication
2:23 Subtraction
3:28 Printing
6:20 Printing mechanism
8:06 History
8:34 Outro

Beaver adding machine

Jaap Scherphuis 2022-07-15 | The Beaver is a very rare adding machine that was made in Japan in 1964. It was exported and sold by Ito-Ya Ltd., a stationery supplies company.

For more information on this and other calculating machines in my collection, please visit my website:
jaapsch.net/mechcalc

0:00 Introduction
0:28 History
1:44 Addition
2:42 Subtraction
4:25 Clearing
4:48 Complementary numbers
5:48 Opening case
8:35 Mechanism
11:02 Outro

The SCM 1011 CB adding machine

Jaap Scherphuis 2022-07-01 | The Smith-Corona-Marchant 1011CB adding machine has a very distinctive styling in orange and brown.

For more information about this machine and others in my collection, please visit my website:
jaapsch.net/mechcalc

0:00 Introduction, History
0:45 Addition
2:10 Clearing input, Non-add
2:51 Subtraction
3:55 Repeat, Multiplication
5:00 More history
5:59 Opening the case
7:29 Paper roll
7:55 Outro

The Precise adding machine

Jaap Scherphuis 2022-06-18 | The Precise adding machine is a simple co-axial adder with a built-in stylus. It was made between 1946 and 1950 in Chicago, and despite its short production period it has a rather complicated history.

For more information about this and other calculating machines in my collection, please visit my website:
jaapsch.net/mechcalc

0:00 Introduction
0:27 Addition
0:54 Clearing
1:22 History
1:41 Precise Developments Co.
2:54 E.C.A.
5:25 Tastee-Freez
7:01 Outro

The Multo mechanical calculator

Jaap Scherphuis 2022-06-03 | The Multo calculator was made in Sweden from 1949 till 1966. It is a model 3, so it has an input display but no back transfer.

Here is a link to @rubberswan's channel with Multo disassembly videos:
youtube.com/user/rubberswan/videos

For more information on this and other calculators in my collection, please visit my website:
jaapsch.net/mechcalc

0:00 Introduction
0:30 History
1:01 Nice touches
1:38 Addition
1:48 Counter
2:24 Multiplication
3:06 Clearing
4:00 Seizing up
6:17 Further history
7:22 Outro

The Everest Plurima Manuale adding machine

Jaap Scherphuis 2022-05-20 | This adding-listing machine was made by Serio in Italy from about 1960 till 1965. It is manually driven, and handles subtraction and negative totals.

For more information about this machine and other calculators in my collection, please visit my website:
jaapsch.net/mechcalc

0:00 Introduction
0:20 Input
0:40 Addition
0:55 (Sub)total
1:59 Non-add
2:24 Subtraction
2:50 Negative totals
3:31 Multiplication
4:50 Ink ribbon
6:20 Opening case
7:05 Outro

The Brunsviga 11S mechanism in action

Jaap Scherphuis 2022-05-10 | This shows the Brunsviga 11S mechanical calculator without its case, calculating 355 divided by 113.

Main video demonstrating the Brunsviga 11S:
youtube.com/watch?v=1wtOBqjVHyA

For more information on this and the other calculators in my collection, please visit my website:
jaapsch.net/mechcalc

The Brunsviga 11S mechanical calculator

Jaap Scherphuis 2022-05-06 | The Brunsviga 11S is an electrically driven mechanical calculator. It is similar to the Brunsviga 11E but with a full keyboard instead of input pins. It has automatic division.

Video of the mechanism:
youtube.com/watch?v=5unqPg0UtWY

For more information about this machine and other calculators in my collection, please visit my website:
jaapsch.net/mechcalc

0:00 Introduction
0:21 History
1:32 Addition
2:13 Subtraction
2:30 Clearing
3:04 Multiplication
4:52 Division
6:20 Outro

The Everest Z5R calculator

Jaap Scherphuis 2022-04-22 | The Everest Z5R is a mechanical calculator made in Italy in the 1950s. It was made by S.A. Serio in Crema. The design is generally similar to the Facit TK, so it uses a pinwheel mechanism, has a 10-key keyboard, and an internal carriage.

For more information on this and other calculators in my collection, please visit my website:
jaapsch.net/mechcalc

0:00 Introduction
0:17 Inputting numbers
0:43 Addition
0:55 Multiplication
1:37 Subtraction
1:47 Shortcut multiplication
2:19 Clearing
2:37 Counter direction
3:45 Division
6:47 Back Transfer
8:43 History
10:24 Outro

The Summira 7 adding machine

Jaap Scherphuis 2022-04-09 | The Summira 7 is a small adding machine. It can do direct subtraction, and was made in West Germany from about 1955 to the mid 1970s. It is very similar to the Resulta.

For more information on this and other calculators in my collection, please visit my website:
jaapsch.net/mechcalc

0:00 Introduction
0:18 Addition
1:07 Clearing
1:55 Small multiplications
2:33 Subtraction
3:53 History
4:42 Outro

Otis Kings Pocket Calculator

Jaap Scherphuis 2022-03-25 | Otis King's Pocket Calculator is a cylindrical slide rule. It was made from about 1922 till the early 1970s. This is a model K from the early 1960, which has just two logarithmic scales which allow you to multiply or divide.

For more information about this and other calculators in my collection, please visit my website:
jaapsch.net/mechcalc

0:00 Introduction
0:31 Description
2:09 Multiplication, Division
5:18 Otis King
6:04 Carbic Limited
7:32 Outro

The Countess adding machine

Jaap Scherphuis 2022-03-11 | The Countess adding machine is a very simple adding machine for British currency. It only does addition, not subtraction. It was made by Summira in Germany in the 1960s or early 1970s.

For more information on this and other machines in my collection, please visit my website:
jaapsch.net/mechcalc

0:00 Introduction
0:14 Columns for currency
1:11 Clearing
1:45 History
2:50 Opening the case
3:38 Carry mechanism
5:48 Outro

The Russian Felix M calculator

Jaap Scherphuis 2022-02-25 | The Felix M is a pinwheel calculator made in Russia from 1929 till 1978 with virtually no change in its design. It is closely modelled on the pinwheel calculator made by Odhner in St. Petersburg before the Russian revolution, because Odhner's machinery was confiscated and used to set up production of the Felix. Millions of these calculators were made.

Errata: The first Felix was probably made in 1929, not 1928, and my Felix-M was probably made in 1976, not 1975.

For more information about this and other calculators in my collection, please visit my website:
jaapsch.net/mechcalc

0:00 Introduction
0:44 The design, addition
1:05 Clearing registers
1:57 Counter, subtraction
2:42 Input clearing
3:11 Reversing direction
4:10 History
5:28 Felix Dzerzhinsky
8:08 Outro

The Precisa 364 adding machine

Jaap Scherphuis 2022-02-15 | The Precisa 364 is an adding listing machine that can also do multiplication. It was made from 1963 to 1978. The Precisa 160 is the same but without the multiplication functionality.

For more information about this and other machines in my collection, please visit my website:
jaapsch.net/mechcalc

0:00 Introduction, Precisa 160
0:41 Precisa 364
1:42 Addition
2:15 Subtotal
2:46 Total
3:10 Subtraction
4:11 Non-add
4:45 Repeated addition
5:04 Clearing input
5:15 Repeated subtraction
6:14 Multiplication
7:08 Negative multiplication
7:36 Squaring
8:21 Shortcut multiplication
9:00 Repeated multiplication
10:45 Opening case
12:10 Outro

The Hasbro Adding Machine

Jaap Scherphuis 2022-02-03 | This is a toy adding machine made by Hasbro in about 1961. It is similar to the Wolverine, but plastic instead of metal.

For more information on this and other machines in my collection, please visit my website:
jaapsch.net/mechcalc

0:00 Introduction
0:19 Unboxing
0:44 Description
1:10 Addition
2:00 Totals bar
2:25 Clearing
3:35 Mechanism
6:19 Patents
6:49 Outro

The American Adding Machine

Jaap Scherphuis 2022-01-26 | The American Adding Machine was made from about 1913 till 1922 by the American Can Company, and for a short while after that by The American Adding Machine Company. The one I show here is the earliest model, which has a gorgeously patterned case.

For more information on this and other calculators in my collection, please visit my website:
jaapsch.net/mechcalc

0:00 Introduction, History
0:54 Input mechanism
1:32 Addition
2:15 Clearing
2:55 History
5:22 Outro

The first and the last Sumlock calculator models

Jaap Scherphuis 2022-01-15 | The Sumlock was made by Bell Punch in the UK from 1940 till the late 60s. It is used exactly like the Comptometer. Here is the first model (1940-1945, made by subsidiary London Computator Corporation) and the last model (1953-1970).

Errata: There are of course 20 shillings in a pound, not 19.

For more information about this machine and others in my collection, please visit my website:
jaapsch.net/mechcalc

0:00 Introduction
0:22 British currency
1:22 Error detection
2:47 Model 913!?
4:22 Model F or SF
4:55 Error on new model
6:00 Outro

The Sumlock mechanical calculator, and some advanced calculation techniques.

Jaap Scherphuis 2022-01-08 | The Sumlock was made by Bell Punch in the UK from 1940 till the late 60s, but these two were made in the early 1950s. They are used exactly like the Comptometer. After a short demo, I show how to multiply the register result by another number, and explain division in a bit more detail.

For more information about this machine and others in my collection, please visit my website:
jaapsch.net/mechcalc

0:00 Introduction
0:26 History
0:59 Overshoot prevention
1:40 Error detection
2:31 Models
2:58 Multiplication
4:59 Division
9:50 Outro

The Mercedes Euklid 16 mechanical calculator

Jaap Scherphuis 2021-12-29 | The Mercedes Euklid 16 is a mechanical calculator that was in production from 1927 till about 1935. The Euklid machines use a unique proportional lever mechanism. This model was the first to use a modular keyboard with tightly packed cubical keytops. It can do automatic division, and has a neat automatic decimal point system for multiplication.

I also have videos of the later Euklid model 29:
youtube.com/watch?v=aVFtFHLIrYM
Video showing the mechanism:
youtube.com/watch?v=nsUWe9KkR8A

For more information on this and other calculators in my collection, please visit my website:
jaapsch.net/mechcalc

0:00 Introduction
0:21 Keyboard
1:00 Crank
1:31 Addition
2:30 Subtraction
3:12 Clearing
3:29 Multiplication
4:48 Decimal points
6:35 Automatic division
9:05 Serial number
9:44 Outro

The Victor 16-83-54 Adding Machine

Jaap Scherphuis 2021-12-18 | The Victor 16-83-54 Adding Machine was made from 1960 till about 1967. It is very similar to the series 6, with a full keyboard, except that some of the controls have moved and are now buttons on the keyboard. This version has an electric motor. I forgot to show subtraction in this video, but that is the same as addition except that you press the minus button.

Here is a previous video about the Victor series 6 and 7 adding machines:
youtube.com/watch?v=Zlh6DEHwe9k

For more information about this and other calculators in my collection, please visit my website:
jaapsch.net/mechcalc

A short history of the Comptometer

Jaap Scherphuis 2021-12-04 | I gave a 10 minute talk at the Gathering for Gardner 12 conference in 2016:

"Before electronic computers and calculators, there were mechanical calculating machines. The Comptometer was one of the most widely used calculating machines, used all around the world for almost 80 years. It quietly changed the world, yet is almost forgotten today."

This video was a practice run I made to see if I got the timing about right. The actual talk was filmed, and can be found here:
youtube.com/watch?v=Q2G-383ij8A

The powerpoint presentation can be found here:
jaapsch.net/g4g/index.htm

For more information about the Comptometer and the other mechanical calculators in my collection, visit my site:
jaapsch.net/mechcalc

The Elm City Counter

Jaap Scherphuis 2021-11-20 | The Elm City Counter is a simple counter, mostly used in the printing and textile industries. It was first made in the early 1880s, but ones like this one that have "C. J. Root Co." on the front were made after 1907. In 1928 the company merged with Veeder to become Veeder-Root, and the inscription of the Elm City Counters were changed appropriately. Production continued at least through the 1930s.

For more information on this and other calculators in my collection, please visit my website:
jaapsch.net/mechcalc

0:00 Introduction, History
3:05 Description
6:01 C. J. Root
8:00 Mechanism
10:06 Outro

The Sirius adder

Jaap Scherphuis 2021-10-31 | The Sirius adder was made Master, who also made the Master and the Business adders. This one has attachments for use in multiplication and even division, but these are completely unusable. The box contains not only instruction manuals, but also various ads, including rather oddly an ad for the Sirius itself.

Video of the Business and Master adders:
youtu.be/m3toHgmCZuk

For more information on this and other machines in my collection, please visit my website:
jaapsch.net/mechcalc

0:00 Introduction
0:53 Addition
1:33 Carry operation
2:14 Clearing
2:39 Scriptor attachments
6:52 Testimonials
7:22 Sirius ad
7:45 Guarantee
8:24 Scriptor instructions
8:52 Special offer
9:32 Instruction booklets
10:54 Ad for Electric Master
11:35 Receipt
12:04 Packing up
13:14 Outro

The Triumphator CRN2 pinwheel mechanical calculator

Jaap Scherphuis 2021-10-08 | The Triumphator CRN2 mechanical calculator is a rather large pinwheel machine. It was in production in Leipzig, East Germany, from 1959 till about 1965.

For more information on this and other calculators in my collection, please visit my website:
jaapsch.net/mechcalc

The Multifix E1R mechanical calculator

Jaap Scherphuis 2021-09-24 | The Multifix E1R mechanical calculator

The Brunsviga D 13Z/1 double calculator

Jaap Scherphuis 2021-09-17 | The Brunsviga D 13Z/1 consists of two calculators, side by side, connected to a single crank. Double calculators like this were used for calculations involving coordinates, such as land surveying, and were also often used by the military. I give a simple example of such a calculation.

For more information about this and other calculators in my collection, please visit my website:
http://www.jaapsch.net/mechcalc

0:00 Introduction
1:14 Uses for double calculators
2:50 Description of the calculation, part 1
3:36 Doing the calculation, part 1
5:24 Description of the calculation, part 2
6:19 Clearing counter and input registers
7:07 Doing the calculation, part 2
9:43 Clearing the output registers
9:56 Manually setting the output registers
10:28 Outro

The Denominator, a pay roll adding machine

Jaap Scherphuis 2021-09-10 | The Denominator is a rare adding machine that simply contains a separate counter for each denomination of US currency. You would go through a stack of pay slips, entering the coins and bills needed for each one, so that at the end you'd know how many coins and bills to take out from the bank to pay your staff. The Denominator Adding Machine Company was founded in 1914 by Frank H. Morse to make this machine. The company still exists today, now called the Denominator Company, and is still making mechanical counters.

For more information an this and other machines in my collection, please visit my website:
jaapsch.net/mechcalc

0:00 Introduction
0:24 What it is used for
0:54 Company history
3:21 How to operate it
3:45 Serial number
4:08 Production
4:39 Opening the machine
6:22 Mechanism
7:55 Repairs
9:23 Outro

Rare Lipsia Addi 7 adding machine with printing mechanism

Jaap Scherphuis 2021-09-03 | The Lipsia Addi 7 was released in 1930, but this variant with a printing mechanism was not success and is therefore quite rare. After the second world war Lipsia was merged with Triumphator, and the Addi 7 was given a makeover and released as the Triumphator KA.

Video of the Triumphator KA: youtu.be/OqqCV5xh3-A

For more information on this and other calculators in my collection, please visit my website:
jaapsch.net/mechcalc

The Precisa 117 mechanical calculator

Jaap Scherphuis 2021-08-29 | The Precisa 117 is a pinwheel calculator with a 10-key keyboard, clearly inspired by the Facit calculators. Its main register and counter are stationary while the input register is on a moving carriage. It was made from 1952 until about 1963.

For more information this and other calculators in my collection, please visit my website:
http://www.jaapsch.net/mechcalc

0:00 Introduction
0:33 Addition
1:35 Clearing
2:15 Subtraction
2:28 Multiply
3:17 Division
5:16 Precisa history
6:44 Serial number
7:02 Outro

A steam engine revolution counter

Jaap Scherphuis 2021-08-14 | This antique revolution counter was very likely used with a steam engine, and probably made in Germany in the 1880s or 1890s. It has an unusual eccentric gear mechanism to drive the units wheel, and is one of the first counters to use the carry mechanism that is in use in almost all odometers made today.

Further research leads me to believe that this counter was made by Schäffer & Budenberg in Buckau.

For more information on this and the mechanical calculators in my collection, please visit my website:
jaapsch.net/mechcalc

0:00 Introduction
0:48 Carry mechanism
1:12 Eccentric gear drive
1:57 Reset mechanism
2:23 History - Eduard Stalmann, Buckau
3:46 Outro

The Facit CA1-13 fully automatic mechanical calculator

Jaap Scherphuis 2021-08-06 | The Facit CA1-13 is a fully automatic electromechanical calculator. Facit made their first fully automatic calculator in 1945, and that evolved into this model which appeared in 1956 and was produced until the early 1970s. As well as the three visible registers it has an internal register used to store the first factor in a multiplication.

I apologise for the wandering focus of my camera.

For more information on this and other calculators in my collection, please visit my website:
jaapsch.net/mechcalc

0:00 Introduction
0:37 Addition
1:08 Clearing
1:28 Semi-automatic multiplication
3:06 Subtraction
4:24 Automatic carriage shift
5:38 Automatic multiplication
8:14 Division
9:52 Aborting division
12:09 The NEG button
13:03 Outro

The Sterling Dial-A-Matic adding machine, 6-dial model

Jaap Scherphuis 2021-07-30 | This Sterling Dial-A-Matic adding machine is a simple rotary adder with six dials and a clearing lever. It was first produced in the mid 1950s.

For more information this and other calculators in my collection, please visit my website:
http://www.jaapsch.net/mechcalc

0:00 Introduction
0:10 The box
0:58 Models
1:19 Stylus
1:37 Addition
2:14 Clearing
4:08 Subtraction
5:05 Outro

The Schubert DRV mechanical calculator

Jaap Scherphuis 2021-07-23 | The Schubert DRV is a very well-designed pinwheel calculator. It was in production from 1952 till the 1970s. The controls are set up so that they can be used with one hand, and designed to need minimal effort. It was designed by Emil Schubert, who had previously co-founded and run Thales.

For more information on this calculator and other machines in my collection, please visit my website:
jaapsch.net/mechcalc

0:00 Introduction
0:20 Addition
0:46 Multiplication, shifting the carriage
2:11 Clearing
4:34 Back Transfer
5:25 Serial number
5:59 History, Emil Schubert
8:03 Models
9:29 Outro

The Ken+Add adding machine

Jaap Scherphuis 2021-07-16 | The Ken+Add is a small dial adder, built into a nice metal case that also contains the stylus. It was named after its designer, Kenneth Pangburn, and made from 1950 until about 1958 or so. It used to have a "Magic Slate" inside the lid of the box, which was a waxy rubbery backing with a plastic semi-transparent film laid on top that you could draw on with the stylus. Peeling up the plastic sheet would erase the drawing.

For more information on this and other calculators in my collection, please visit my website:
jaapsch.net/mechcalc

0:00 Introduction
0:32 Addition
1:30 Subtraction
1:55 Clearing
2:26 History
3:20 Magic Slate
4:15 Patents
4:40 Similar machines
5:09 Outro

The Antares P4 mechanical calculator

Jaap Scherphuis 2021-07-09 | The Antares P4 is a pinwheel calculator made by the Italian company Organizzazione Pozzi in the 1950s.

For more information on this and other calculators in my collection, please visit my website:
jaapsch.net/mechcalc

0:00 History
0:20 Models
1:55 Addition
2:11 Counter
2:35 Clearing
3:09 Serial number
3:45 Colours
4:15 Further history
4:58 Outro

How the Original Odhner pinwheel calculator works

Jaap Scherphuis 2021-07-03 | I'll show and describe how an Odhner pinwheel calculator works. It is an Original Odhner model 24.

For more information about this and other calculators in my collection, please visit my website:
jaapsch.net/mechcalc

0:00 Introduction
0:29 Pinwheel
1:14 Carry mechanism
3:27 Latch
4:26 Input clearing mechanism
7:00 Counter increment mechanism
10:45 Counter carry mechanism
13:34 Back transfer mechanism
15:20 Input display mechanism
16:02 Outro

The Original-Odhner 24 mechanical calculator

Jaap Scherphuis 2021-07-03 | The Original-Odhner model 24 is a mechanical calculator with a pinwheel mechanism. It has a large capacity of 20 digits, and a back transfer mechanism. It was made in Göteborg in Sweden from 1940 (or maybe a bit earlier) until about 1948.

In 1875 Willgodt Odhner made the pinwheel calculator that was the ancestor of almost all pinwheel machines that came after it. He died in 1905, after which his sons took over his calculator production business. It was they who moved to Sweden when the business was taken over after the Russian revolution (NOTE: In the video erroneously imply that Willgodt moved to Sweden).

For more information on this and other calculators in my collection, please visit my website:
jaapsch.net/mechcalc

0:00 Introduction
0:19 History
2:10 Addition
2:42 Subtraction
2:57 Clearing register and counter
3:07 Multiplication
4:17 Clearing input
5:25 Counter
6:13 Division
8:02 Main carry mechanism
9:27 Counter carry mechanism
10:13 Back transfer mechanism
11:36 Outro

The Calculator adding machine

Jaap Scherphuis 2021-06-18 | The Calculator adding machine was made between 1915 and 1922, at which point it was replaced by the Lightning Calculator. It is almost identical to the Bonham & Schram calculator from 1905.

For more information on this and other calculators in my collection, please visit my website:
jaapsch.net/mechcalc

0:00 History
1:02 Stand and stylus
1:18 How to use
2:50 Stand and stylus
3:35 Further history
4:02 Outro

The SIMEX Caroline adding machine

Jaap Scherphuis 2021-06-11 | The Caroline is a simple adding machine originally made by Simex. The one shown here is the more common French licenced copy. It was made in the 1960s. It's mechanism is very similar to the Addipresto/Addimat.

Addimat video: youtube.com/watch?v=hIuxwschXg0

For more information on this and other calculators in my collection, please visit my website:
jaapsch.net/mechcalc

0:00 History
1:15 How to use
1:56 Carry mechanism
2:16 Clearing
2:34 History
3:22 Mechanism
6:13 Outro

The Melitta VII/16 pinwheel calculator

Jaap Scherphuis 2021-06-04 | The Melitta VII/16 is a mechanical calculator with a pinwheel mechanism, which was made in East Germany from 1955 till at least 1963. It has a unique input mechanism with input pins that remain stationary when you turn the crank.

For more information on this and other calculators in my collection, please visit my website:
jaapsch.net/mechcalc

0:00 Introduction
0:18 Input mechanism
1:34 Addition, multiplication
2:48 History
6:41 Clearing
7:30 Division
9:54 Back transfer
11:44 Carriage release
12:30 Outro

The Madas Portable 12e mechanical calculator

Jaap Scherphuis 2021-05-30 | The Madas Portable 12e is a mechanical calculator made by H. W. Egli in Switzerland from 1931. Versions of this machine were made until the late 1960s. This is the simplest electric model, and most later machines were much more automated. Even though this model is electric, shifting the carriage is still done manually. For this reason it has no fully automatic division

For more information on this and other machines in my collection, please visit my website:
jaapsch.net/mechcalc

0:00 History
1:50 Addition
2:24 Subtraction
2:42 Clearing
2:49 Multiplication
4:32 Division
6:53 Manual crank
7:32 Removing carriage
8:08 Serial number
8:34 Outro

The Madas BZS mechanical calculator

Jaap Scherphuis 2021-05-22 | The Madas BZS is a mechanical calculator made by H. W. Egli in Switzerland. The first version of the Madas Portable is from 1931, but this fully automatic one is from about 1960. It has fully automatic division and multiplication. Note however that I have not been able to get the multiplication working, as it seems that some parts deep inside are stuck together and I have not yet dared to take it apart far enough to reach those parts.

For more information on this and other machines in my collection, please visit my website:
jaapsch.net/mechcalc

0:00 Introduction
0:16 Addition
0:41 Subtraction
1:03 Semi-automatic multiplication
2:04 Clearing
2:22 Division
3:42 Tabulation
4:55 Aborting division
6:25 Counter direction
7:00 Setting multiplier
8:06 Automatic multiplication
9:12 Carry mechanism
10:24 Split register
11:10 Decimal markers
11:40 Outro

The mechanism of the EOS mechanical calculator

Jaap Scherphuis 2021-05-08 | The EOS calculator is identical to the Hannovera CK calculator. It uses an oscillating segment system somewhat similar to the Demos, but whereas the Demos uses complementary digits for subtraction, the EOS allows you to simply turn the crank in the opposite direction like a pinwheel machine. About 1000 were produced, and sold in Switzerland.

I demonstrate the EOS in the following video: youtu.be/_bmuSqlPrL8

For more information on this and other calculators in my collection, please visit my website:
jaapsch.net/mechcalc

0:00 Introduction
0:39 Addition cycle
3:28 Subtraction cycle
5:11 Oscillating mechanism
5:40 Counter mechanism
7:07 Automatic input clearing
7:52 Clearing output register
8:17 Cam wheels
9:24 Outro

The EOS mechanical calculator

Jaap Scherphuis 2021-05-08 | The EOS calculator is identical to the Hannovera model CK, but was made for the Swiss market. It uses an oscillating toothed segment mechanism which was easier to manufacture and did not infringe on Brunsviga's patents, unlike Hannovera's previous models which were pinwheel machines. The mechanism is similar to that of the Demos, but better because it can do subtraction by turning the crank in reverse.

I show the mechanism of the EOS in another video: youtu.be/pWOyLou-uys

For more information on this and other machines in my collection, please visit my website:
jaapsch.net/mechcalc

0:00 Introduction, History
1:28 Addition
2:58 Subtraction
3:21 Counter
3:50 Clearing
4:20 Shifting the carriage
5:39 Serial number
6:52 Outro