I purchased an eco model 94 and when I was checking it out I noticed a painted over label on the side of the wall mount bracket. After I cleaned it off it turned out to be a brass tag that was glued on that reads: BUICK MOTOR DIV. GEN. MOTORS CORP. MACH. NO. 122636. This is stamped or engraved on the brass. The serial number for the meter is 4 N2721 spec. no. 94 1001.
I believe it may have come out of the GM proving grounds in Michigan since the previous owner was imployed there many years ago. Anyone ever seen one of these?

Wally

Having worked for GM for over 26 years, I can tell you that there was a time where absolutely everything they owned was tagged with a brass tag. From desks to filing cabinets.

So your story is probably true - esp. since it was buried under multiple layers of paint.

Jim