Calculating - Plus (London Computator Corporation)
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Plus
Model   LC/509/SF/4920
Maker   The London Computator Corporation Ltd
Origin   39, St. James's St. London. S.W.1.
Date   1950s
Serial    
 
This adding machine probably dates from the 1950s although the design is some twenty years older. It is adapted for the old UK sterling currency of pounds, shillings and pence. Each column of keys has the numbers 1 to 5. Starting from the left, there are three columns of green keys and two of white ones for pounds, green keys for shillings (including a separate one for ten shillings) and white ones for pennies, halfpennies and farthings.
 
The lack of numbers greater than five means that an experienced operator can work very quickly without looking at the keys, a bit like touch typing. To key in a higher number, the operator presses two keys. If two keys in the same column are pressed at the same time, only the lower one registers. But if two keys in different columns are pressed together, both register. The keys on the odd number rows are more deeply recessed than those on the even rows.
     
The small levers on the display can be moved up or cleared down to make the numbers easier to read. The result shown here is £6,113 12s 3¾d and the maximum is £999,999 19s 11¾d. The lever next to the ½ key is used to clear the result display to zero. This machine can only be used to add but larger versions with the full range of numbers could also subtract while multiplication and division were possible with practice.
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
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