Only have one Magnatek ballast here, it's an H33, and it's the only one I have with a capacitor with a metal housing, I'll look later and see whos name is stamped on it.

I do however have a couple of 15uF caps made by Aerovox, they came with the M138 ballasts, but they too have the typical plastic round encasing. Tried one of those caps to fire up different halide bulbs, while they fired okay the 22.5uF cap really cranks them up a notch.

But I did put a meter on them and they came in with 5% of their rated 15uF.

Think someone just tossed that cap on that ballast for you

All of the caps that shipped with my Advance ballasts have the Advance name printed on them. Not sure if they make their own or just rebrand someone elses.