Finally succeeded at posting a pic. My RCA 28x5 has four or five caps that look similar to this. What type is it? (eg, mica, etc). A couple of these have values that vary 30-50% from specs. Are these of a type that should be routinely replaced, or only if values are off? .

It is a blurry capacitor. Often assembled by people with bad eyesight.

Seriously, I've never seen one like that, but the construction looks like something you would expect to be a mica capacitor (constructed like a non-variable version of a trimmer cap). Replacement is your call. If it is in a circuit that would care about 30-50% value shift, it is probably a good idea.

Curtis Eickerman