Fuel Cap Finish, I'm over thinking again... Options

[bbrock]

I'm pretty sure I've seen a thread on this but I couldn't find it with search. All of he survivor and reference photos show the cap being dull silver with what appears to be a plain zinc finish - same as mine. But when I inspected my cap, I found traces of what sure looks like cad/yellow chromate under the tangs. Now here's the over thinking... yellow dichromate is not that durable and easily removed with many solvents or worn off. Is it possible these caps started with a yellow chromate finish that was soon lost due to a combination of fuel vapor and hand wear? For those who saw these cars fresh off the boat, what is your recollection?

It's a little hard to tell in these pics, but in good sunlight, the color under the tangs is iridescent yellow and looks exactly like cad/yellow zinc.

[bbrock]

Right or wrong, mine looks like this now. A few things I can say about my cap. It is stamped with the VW logo so I assume it is OEM. I can't rule out it being a replacement but I've owned the car since 1984 and I don't recall it showing up in the extensive stack of receipts dating back to 1978 from the PO. I will double check that. The original finish on this cap was zinc with a yellow chromate coating. I know it was zinc because 5% muriatic acid took the original finish off and from what I've read, it would not have taken cadmium off. I'm 99% certain there was a yellow chromate coating because of the traces that remained under the tangs and inside the cap. I don't know if it is the original cap that came on the car, but it is now restored to its original finish. Easy to reverse back to bright zinc if I want.