I popped the hood on my '91 300-SEL. I see the 2 valves you outlined in your photo. Mine have MB parts numbers and some other identifier on the bottom side. It's dark and I was using a weak flashlight. The numbers appear to have faded with age.

I will take another look when I have better light in the A.M. and let you know what I do or don't see.

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Mike Murrell
1991 300-SEL - Model 126
M103 - SOHC
"Fräulein"

I appreciate that, the numbers on mine are impossible to read. But don't take it of to have a better look, the nipple is supper brittle and will break. I found one at the JY and it broke instantly as well when I took it of. The only numbers I could read on the one at the JY were the first six numbers: 001 140 XXXX.

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1979 Black on Black, 300CD (sold), 1990 Black 300SE, Silver 1989 Volvo 780, 1988 300CE (vanished by the hands of a girlfriend), 1992 300CE (Rescue).