Filip,
That does not appear to be the check valve from the air tank under the left front fender.
Hi.
This is one of his listings... Mercedes W100 600 Luftfederung Gummikappe für Druckregler 0 481 040 002 | eBay he has all the stuff you need.
600 #796 (1967 US version)
300SEL 6.3 #1285 (1969 EURO version)
300SEL 6.3 #5346 (1971 US version project)
One of our members, Thomas aka tcj-old has produced replacement check valves for the air tank in the fender. I can't find a name and member information to ask if there are any left. Anybody help?
Jack