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.