Rubber stopper on window channel?

[Tubby]

I have a 1939 Tudor Deluxe. I am replacing the rear window. I am about to reinstall the window. Searching the forum I found helpful instructions. One of the threads showed someone installing rubber washers onto the window channel stop: https://www.fordbarn.com/forum/showt...w+installation

I have included pictures of the stop on my channel as removed from the car. There is no rubber evident.

Does anyone know if there is supposed to be rubber on this stop? I think you can appreciate that I only want to do this installation once!