Group, can anybody tell me who the supplier was for the 1958 and 1959 (and maybe later) Chevrolet accessory locking gas cap, p.n. 987741?

I have one in a retail vintage box direct from the supplier, and I know this supplier provided FoMoCo's caps. They were headquartered in the Detroit area, so they may have also supplied GM.

Or can anybody point me to a clear photo of the genuine, vintage accessory item?

Thanks in advance for any clues.