I replaced my windshield post seals with genuine MB parts and there is no "cloth covering". I don't know if it indicates a change or if the "cloth" is embedded under a final layer of rubber. They are definitely slicker and a bit harder than the softer aftermarket rubber parts that I bought from Miller's. They were an immediate fix for the binding that those parts caused. Window now goes up and down with ease as it should.
The MB parts were coated with a tough yet flaky parafin-like coating. It was chalky in color, flaked like giant dandruff, yet was very hard to completely remove. I left the coating material in the groove as it seems to reduce friction.
Ray
'68 280SL 4-spd Coupe