Does anyone have any facts on when, or if, stainless steel one piece wheel covers were ever used on Pagoda's???
My car, late January 1969 build, also had steel wheel covers, chrome plated. I do know that replacements I bought, OEM from MB (complete with holographic authenticity sticker on the back) were stainless steel. I've pointed this out before, but there is a huge difference between the reproduction stainless steel wheel covers, and OEM. I believe any reproductions are being sold under the radar, since they have the three point star and would violate Mercedes-Benz trademark. However, there were plenty made and sold before they put a stop to official sales of these. The OEM's are a much higher grade of stainless, and thicker gauge. They are polished like jewelry. There's a distinct color difference too--the reproductions are "cooler" and the OEM's are "warmer". What exactly the alloy difference is, I don't know. But in terms of desirability, once you see the OEM's compared to the repros, the OEMs should win your heart each time. In the attached photo, the OEM is on the left, the repro on the right. I tried polishing the repro using a buffing wheel and many grades of metal polish, and couldn't come close to the finish of the OEM. At the time I needed wheel covers, the repros were selling for $79 each and the OEMs for $129.00. I opted for all OEMs.
Everyone's tolerance for cost, and for authenticity is different. I can tell you with certainty, that unless you are starting with a chrome plated steel cover that isn't too far gone, it will be quite costly to have wheel covers chrome plated.
When I wash my car these days, I generally remove the wheel covers and hand wash in a sink and dry them--no abrasives, no brushes. I don't think many people did that in the 60s and thus much of the backside rusted severely.
As for stainless steel, I'd like to think that Mercedes-Benz, when specifying the wheel covers, probably put some thought into appearance and longevity. The repros were probably done to a price point. Since there are three basic forms of stainless steel (Martensitic, Austenitic and Ferritic) and literally dozens of grades within each form--this is best left to a metallurgist to figure out!