Coming back to the stripped panels of the Comptometer. The side-panels came out good enough from underneath the brown refurbishment paint, won't be touched. The top-panel was however a (1940-ies?) replacement part without any copper-plating. Also the front display-panel was very worn, so these two top panels were up for repainting.
To select a fair color-match, took a panel to the auto-materials shop. Browsing the shelves with spray-cans, a decent match was found in Motip number 51350. At least, the lid of the can looked closest.
The panels were de-greased, with soapy warm water. The top-front display-panel was sanded down with fine waterproof sandpaper, to remove the rust. It shows all the layers that were worn through, from use. The cork riveted inside the top-panel was taped off.
First a grey primer was applied to both parts. Then two or three fairly thin layers of the metallic-brown lacquer was applied. The lacquer is translucent, so the finish gets darker with every layer. The front display-panel got more layers than the larger panel - and is probably the 'final' color of this brown metallic lacquer.
Metallic paint is fairly vulnerable, so a layer of clear-coat lacquer added to finish the panels. The main panel shows some color variations from thickness differences; translucent lacquer needs a lot of care to get an even finish (and me a lot more practice). Not too bad though, when viewed from a distance it isn't too disturbing.
Overall, the difference with the side-panels is probably smaller than the color differences within original panels.
All probably too much effort to be put into a pretty common 8-column model H Comptometer, but a fun project - and it'll look nice again :)