It looked quite awful, so the housing was taken completely apart. A mottled greyish-brown paint was all over the machine, almost certainly applied during an overhaul in the 1940s or early 1950s. At that time, many old Comptometers were re-furbished (scroll down to 'refurbed machines'), both by Felt & Tarrant distributors and by others. (Oh, and I can confirm that the four sides were not separated for the spray-painting on this one.)
The cork that is glued to the inside of the side-panels (sound-dampening) can be removed - using a sharp putty-knife to break the brittle glue and carefully bending the cork sheets to release them from the fold-over flanges. The top-plate cork is riveted, so that is left on the panel.
To strip-off the old refurbishing paint, a set-up with lye is used. The stripping-tray is the first step; that is a baking-tray with lye or sodium hydroxide or drain-cleaner - on the right. The mixture is made with about 50 to 60 gram of NaOH pellets per litre of water (a bit over 1M) and stir gently with a plastic or wooden spoon. When the solution turns clear again, it's ready for the parts to be placed in the solution.