On Mar 10, 2017, John Tygart in Syracuse, USA wrote:
"I have a NOS in the box tach number RN 2350/01. Even sitting in a box the case was still showing some rust. I think most of these were not truly plated but "pickled" in an acid solution. Dipped my case in some mild phosphoric acid to remove the rust, and in 5 minutes was completely bare metal. Decided to refinish it to match the speedometer case with was a flat black. Zinc plated it and did a clear enamel to preserve the reflective inside and then sprayed the outside flat black to match my original speedometer. The black case on the speedometer has a white inside coat".