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I well remember buying my first calculator. It cost a fortune and had a red light-
emitting diode display which was so bright you could almost read in bed with it
under the covers. As a result it went through batteries like there was no tomorrow
and, even today, I am still conditioned to switch off a calculator when not in use…
except often there’s no off switch. The year was 1974. The model was a Sinclair
Scientific.This month’s exhibit isn’t really a calculator… it’s an adding machine. And a fairly specialised one at that. It’s for totting up money. Old money. It was used at Associated Dental Products in Purton in the 1950s and donated to the Museum in 1987 by Mr Donald Cakebread of Purton Stoke.
If you look on the Museum website you’ll see a clearer picture: it has keys of three different colours, generally running from bottom to top from 1 up to 9, except for the final right hand column – which only has five buttons: ¼, ½, ¾, 10 and 11 – and the 6th column which consists only of 1’s: these give us the clue to its specialism in that it was for adding up columns of figures in pounds, shillings and old pence. The maximum amount that you could enter was £99,999:19s:11¾d.
When you pressed a button in the appropriate column it stayed pressed and you could see the amount in the depressed keys. 9s was made by having the 9 in column 7 pressed, but this was 19s if its corresponding 1 in column 6 was also pressed. When the amount was right, you would pull the handle towards you, there would be a whirring noise and typewriter keys would fly up from the top section to hit a strip of till roll paper at the very top of the picture.
Other red buttons at the top of the keyboard allowed different functions: subtract the amount, clear, sub total and total. No electrics, no batteries, no wires… just cogs. But it was useless if you had run out of till rolls. A different world in so many ways!
Click here if you want to see a clearer picture of the adding machine.