The Underwood 300R adding machine

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:
www.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

[@DaveInBridport]

I always find these machines fascinating...

[@stephenfreeborn]

Nice video. When I worked as a movie theater and used the adding machine to close out the tills, I used an electronic listing adding machine. I never understood why the user interface was so different than a calculator. I imagine that the interface from machines like this carried over to modern adding machines.

[@jaapsch2]

Absolutely. GrumpyTim just posted a demo of an early electronic desktop calculator which uses the adding machine interface. It even has T and S buttons for totals/subtotals. I have an Anita 811 pocket calculator from 1972 that also still does addition/subtraction in that way. It took a while till the syntax was changed to what is now standard. It may have been Casio that popularised that change.

[@GrumpyTim]

Hi Jaap, I first watched this on a smart TV, where you don't get to see the written description and so on - I was thinking "that's got to be an Olivetti in different clothes, it's identical on the inside!". Now I'm back on the computer I can actually read what you had written. Great little machine, and that one looks like it's in pretty good condition too.

[@alanesq1]

I watched it on a laptop but didn't see any text, I enjoyed anyway it as a video for those who understand ;-)

[@GrumpyTim]

@@alanesq1 Hi Alan, I was only meaning the written bit in the description that you can see below the video on your computer (if you're not viewing full screen). On the smart TV's (or at least using a Fire Stick) that info is either difficult to access or totally impossible to access, the same as when a KZbinr says "I'll put a link on screen" - those don't appear on a smart tv - no idea whey not. You'll have definitely spotted that fact it was an Olivetti in different clothes.

[@lizzyfrizzy4969]

Mistake lever? Neat

[@MattMcIrvin]

It's interesting that by the end of the era of mechanical calculators, adding machines had basically standardized on this somewhat odd user interface, and it was by far the most common type of general-purpose mechanical calculator. I remember encountering one at my grandparents' house. In some ways it's worse than much older mechanical calculators: you can't see the number you're entering at all, and the only way of even getting a total is by printing it. And it's hopeless for division. But it does make it not hard to do a multiplication if you know what you're doing, though the output is a bit awkward.