



We had one of these when I was only a child, probably 1960 or earlier. It is a mechanical calculator of sorts. This is not my childhood one, but thanks to people like Noeline who put these items up for auction rather than throwing them out, I was able to purchase it just last week(May 2008).
With no user manual, it was a test of memory to work out addition (easy) and subtraction (slightly harder)  it’s only two functions. The front side (shown above) is for addition, you flip the unit forward and down to get at the reverse which handles subtraction. You might also see the handle right at the top of the unit, you pull it up to clear the results display  the series of small holes near the top. Under the handle you pull out to clear the unit is the serial number  A725526. It was made in Germany.
The green stylus has a metal point on one end for using the unit, and a propelling pencil on the other end.
I took a series of photographs showing the unit in more detail, and then an example of addition and subtraction. A computer it isn’t, but Yesterday’s Technology it most definitely is.





The Addiator comes in a very presentable leather case.




The stylus is a bit motheaten, it seems to have been etched both ends. I suspect it is the acid from fingers left on the unit for years.


The two images below show the unit opened out for subtraction



Below, we see the handle pulled up to clear the results display.


To add 22 to 66 is quite simple. You first place the stylus in the ‘2’ digit in the rightmost column and simply pull downwards to slide the internal bar down until the stylus stops at the bottom, whereupon the display shows a ‘2’ in the column. We then repeat this for the second column (the 10’s column). The display then shows ‘22’.



We now have the ‘22’ on the display. To add ‘66’ to it, we put the stylus in the ‘6’ digit in the rightmost column and pull down. When the stylus stops at the bottom the display shows ‘28’. Repeat the operation in the second column and the display shows ‘88’, the result of ‘22’ and ‘66’.



Performing an addition that requires a ‘carry’ digit is only marginally harder. We will start with ‘99’ and add ‘1’ to it, for the expected result of ‘100’. Again, we start in the rightmost column, put the stylus in the ‘9’ hole and pull down, then repeat for the second columdn. The display shows ‘99’.


It gets slightly trickier here. We want to add ‘1’ to the result, so as usual we put the stylus in the ‘1’ hole and pull down. However, this time when we pull it down, a little red ‘plus’ sign shows in the display  this tells us we have a ‘carry’ digit, so without removing the stylus we move the stylus UP and round the little corner at the top and slightly down, which has the effect of adding ‘1’ into the next column. That column in turn now shows a red ‘plus’, so we know we have a ‘carry’ digit there too. Since we have nothing further to add in the column, we put the stylus in the ‘0’ hole and move it up and round the little corner, which then leaves the display with ‘100’, the result we wanted.





Subtraction was awkward, so I suspected I was doing something wrong. It’s the starting position that didn’t feel right. With the unit flipped over to the ‘subtraction’ side I was having to enter the digits as ‘9’ if I wanted ‘1’, etc. Then I had an Aha! moment and turned the unit back to the addition side, enter the ‘100’ as if I was going to add something to it, then turned it back to the subtraction side, and voila!, there was ‘100’ on the display. So to subtract ‘1’ from ‘100’ we enter the ‘100’ as above and then on the subtraction side, put the stylus in the ‘1’ hole and pull down. The red ‘plus’ shows, so we instead move the stylus up and around to perform the ‘carry’ (underflow in this case). The red ‘plus’ now shows in the second column, so we put the stylus in the ‘0’ position in the second column and move up and around, so that the display now shows ‘99’ as we would expect.
While the red ‘plus’ is obvious, in fact when you put the stylus in a hole, if the hole is currently red, you know at that point carry is required, so you can do the ‘up and over’ operation directly.





Cute, huh?


