Topic: Gas Cap Gasket?

[Zi.gg.y]

Hello everybody and sorry if my English is not perfect...

Got myself a SJ C-Code Convertible and when I had it in my garage there was a strong smell of gas. So I checked the Gas Cap and found what I thought is a worn out rubber gasket (pic below). So I ordered a replacement like this https://www.npdlink.com/product/gasket-fuel-cap/106665 which was much larger than I expected. As I tried to tear of the old gasket, I realized its not rubber but maybe paper? Plus the part I thought was worn of is pretty symmetrical, it seems to be fabricated this way?

So now I'm confused. Do need this strange gasket maybe for ventilation purposes? Why is the replacement so much different? Do I need both?
Or is the larger rubber replacement the better solution for a driver car and a small paper/leather gasket would be concours? I couldn't find pictures what the gasket looks like on a NOS Gas Cap nor have I found a gasket that looks like mine.

[J_Speegle]

Has really nothing to do with the venting process other than to seal the cap to the filler neck. The venting is done through that small hole in the center that you can see in your picture

Think the original material was a leather based one. Not sure why the reproducers chose rubber other than its cheaper and easier to put on an old cap without disassembling. Reproductions are often different to keep costs down, don't believe or have found that enough buyers don't want to spend what it would take to make them correctly, original material is not available or legal, or they can't find anyone to make them like they did originally

Close up of an original

[Zi.gg.y]

Thanks Jeff for the picture of an original.
I suppose then the repro from NPD has a much larger outer diameter because it's maybe a one size fits all. Vehicle Information for the product mentions quite a lot of cars, from 1965 Mustang up to 1982 Bronco.