Axial electrolytic
approx 0.5 inch (12 mm) diam, 1.0 inch (25 mm) length

Markings:
HGC
CP-C
2J104K
123

Google tells me it's a 0.1uF, but I can't find a reference for the "2J"
voltage rating. And, any idea what the other markings are?

There are no manufacturer markings (logo, etc.), just plain gray shrink
tubing with the above alphanumeric markings.

This is used in a single-phase 240VAC low current box fan speed controller (1
TRIAC is the main current controller).

Any help would be greatly appreciated.

Thanks,
--
John English