Uploaded April 2023 | Updated September 2026, 1 hour ago
The Underwood 300R adding machine was made from 1962 till about 1971. At this time Underwood was owned by Olivetti, and this is essentially an Olivetti Summa Quanta 20 with a different casing.
I forgot to demonstrate the button with the triangle symbol. This is the non-add button, which prints the entered number without changing the current total in the register.
For more information about this and other machines in my collection, please visit my website:
jaapsch.net/mechcalc
0:00 Addition
0:25 Input and clearing
0:46 Subtraction
1:10 Indicator
1:17 Multiplication
1:42 Printing in slow-motion
2:00 Ink ribbon
2:19 Mechanism
2:46 Outro
The Underwood 300R adding machine was made from 1962 till about 1971. At this time Underwood was owned by Olivetti, and this is essentially an Olivetti Summa Quanta 20 with a different casing.
I forgot to demonstrate the button with the triangle symbol. This is the non-add button, which prints the entered number without changing the current total in the register.
For more information about this and other machines in my collection, please visit my website:
jaapsch.net/mechcalc
0:00 Addition
0:25 Input and clearing
0:46 Subtraction
1:10 Indicator
1:17 Multiplication
1:42 Printing in slow-motion
2:00 Ink ribbon
2:19 Mechanism
2:46 Outro
