Yes, 35 year old plastic that gets pelted by road debris and UV rays. They are near impossible to remove without breaking them. This is an item I'd try to buy new if possible.
Agreed. Unfortunately they aren't made anymore. Most owners apparently remove the boards and throw them away. Other than buying a used endcap my only alternative is to scan the one on my '97 and 3D print one. Can you send me a picture of the one you have? I'm OK with some dents and nicks.