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Please help identify this component. It is cylindrical, with an axial configuration, and no obvious indication of which end is which. The writing on it is: K25U 104M 50V 8502
The 104M makes me think it is a 0.1 uF capacitor, but, in my extremely limited experience, this is an unusual form factor for a capacitor. My googling for images of similar looking capacitors has turned up nothing.
I think your guess is right. From the code and appearance, it should be: an unpolarized, 100nF, ±20% tolerance (from the "M"), 50V capacitor. That form factor is not unusual for older capacitors, and the physical size makes sense for a 100nF 50V cap.
Also, if that "8502" is a date code, that would be January 1985!
To verify (or at least narrow down) whether it's a capacitor or not, you could check resistance in both directions. If there's no conductivity in either direction, it's very probably a capacitor. If not, then it's either a broken capacitor or something else entirely.
Edit: For completeness, a datasheet search for "K25U" turns up a couple things:
It appears to be an axial molded ceramic capacitor - 100nF +/- 20% (M) 50 V rating.
It was likely manufactured in January of 1985.
Here (page 106) you can see some similar types.
I don't see a datasheet reference to that part number on the net, but I would guess it might be Z5U dielectric from the 'U' in the part number, value/rating and the age. If so, you could expect it to be very unstable with temperature and time (and change drastically with applied voltage)
