I'd like to try to help but I don't know what you mean by the face plate. I have a copy of a service manual and there's nothing in there called that. Scrolling through the parts list I see several different C501s and 502s, so which one you want depends on what it's used for.
The detachable head of the radio is called the display unit, and that could be called its face. In that case, it's a 100 microfarad, solid tantalum. "S.TAN TEESVD 1C 107M12R" That's on the back side of the display/VR board.
W4ATM - 35 Miles south of the Kennedy Space Center
Retired RF Design Engineer
Now able to play with all the hobbies I never had enough time for