To start the re-assembly of the Comptometer, they newly-lacquered key-plate is mounted back onto the mechanism. Before doing that, the red controlled-key button must be mounted (insert stem from underneath through hole and press the button on the stem).
Also the name-plate has to be mounted first; this is screwed not onto the key-plate, but it is screwed into large washers that also serve to hold the cork lining in place. In practice with old machines, these washers will be 'glued' onto the cork and the plate could perhaps be screwed of safely - however there is also a risk the large washer will drop free and deep into the mechanism (and then no way to re-mount the name-plate without a full disassembly and taking off all keys!).
The key-plate having been prepared, the front of the plate is hooked under the two tabs at either side of the carry-suppression levers.