Hello Bob,
I am not going to help you or anybody else. Otherwise you can repair the cap at low cost and I won't find any good one on ebay or so anymore ...
Of course, I am kidding.
As the others already mentioned, it'll be no cheap operation. Finding a good and reasonable plating service (perhaps in Mexico) will be the biggest burden.
The others are also right, you have found the absolute correct YMOS gas cap. The other gas caps (HUF) won't work, they cannot be disassembled. :|
On your 2nd picture with removed cork gasket, you can see one of the two little holes. Underneath one of it it a little metal plate which needs to be moved to one side with a stiff needle or sharp nail. Then you can pull off the upper non-chromed cap from the heavy main lower body which goes into the fuel-filler neck. Everything else will be straight forward.
The best is to dissassemble the gas-cap unit in a large cardboard box or pan so that you won't loose any of the little parts.
Then you need to remove one retaining ring/spring in order to remove the lock cylinder.
I am sorry, currently I don't see a possibility to get your gas-cap cylinder re-keyed . For this you need the original YMOS parts (cylinder and locking plates) together with the correct key. The latter is easy but the original YMOS parts are nowhere available - at least I am not aware of and they are not factory-avaible at VALEO in Heiligenhaus/Germany, the mother company of (former) YMOS, either.
As to your outer cap ("free-spin collar"), there have long, long been some ebay offers in Germany (
www.ebay.de) which just offered that part: brand new and chrome-plated. The guy I bought mine from claimed these would be original DaimlerChrysler parts sold in the 60ies. But I doubt this being true. I have never heard from that claim before, no MB info anywhere on that. I rather believe these are more recent Eastern European reproductions. But they look damned good. I paid 25 Euros for each. Maybe you might be able to find the one or other still offered on ebay.
Anyway, good luck to your "surgery"
All the best,
Achim
Achim
(Magdeburg, Germany)