The tale of 3 gas caps

OK, first off, I am a swap meet vendor who really tries to sell the correct part for the correct car. Those MOPAR, Chevy, Ford guys really spend a lot of time at my space researching the exact part markings. If you are a Corvette owner with an NCRS book in your hand, you know what I am talking about. Here are three caps with the same part number, Dole DGF 41, or Stant 10646, or Gates 31646. #3 is marked Pressure Vacuum; #2 is not marked and I assume not vented, #1 is marked Vented, Anti Surge. Each has the "S" mark stamped in the center rivet and the SM stamped on the wing. So the real question is; are these original caps that fit NOS criteria, or an after market, and what cars would they fit? I have the Stant application that fits 16 cars and various models. Also, there are those caps that have no markings at all. BTW, these are from a very old inventory. Any help is greatly appreciated.

Thanks

Dan

dlmarx@bellsouth.net

The part numbers given refer to cap #1. These are aftermarket parts and they can be bought at a auto part store with that part number. See link for apps.

http://www.gates.com/part_locator/reverselookup.cfm?requesttimeout=500

Picture #3 has an additional marking on the reverse side where the "SM" logo is marked. The numbers "3118" are stamped on it. See pix. Does this have a specific part number that goes with this cap? I have tried to locate a number, assuming it is GM.

Dan