I've replaced two Mercedes windshields in the past three decades. The first was on my old Ponton 180 in 1988. The second was by a glass-shop on my '82 240D in 2009. Both times the gasket was from Mercedes. NEVER AGAIN!
The OE gaskets are too old and have obviously been sitting on the shelf way too long. Both of mine cracked & rotted after a just few years until they looked nearly as bad as the original, 27-29 year-old gaskets. Next time, I'm letting the glass shop deal with getting their gasket to fit.

Happy Motoring, Mark

__________________
DrDKW