Identification of capacitors

[Mr_Project]

Hello, this is my first post to this forum.  I build high voltage projects in my spare time. I recently purchased a couple capacitors and if anyone could give me any information on their material that be helpful. Thank you.

[Mads Barnkob]

The black encapsulating material reminds me of the round RF MICA capacitors from the same age. But with its 10KVDC rating and no mention of maximum cycles per second or frequency makes me guess this is some sort of energy storage / smoothing capacitor for a high voltage power supply, not a resonant tank capacitor.

[Mr_Project]

I was told by their previous owner, that they were off of some transmitter. I've also got a couple 32kvdc  that came froma radar  that look similar. I was thinking maybe mika.

[imp]

The black encapsulating material reminds me of the round RF MICA capacitors from the same age. But with its 10KVDC rating and no mention of maximum cycles per second or frequency makes me guess this is some sort of energy storage / smoothing capacitor for a high voltage power supply, not a resonant tank capacitor.

What particular factors would affect a high-voltage mica dielectric capacitor regarding operable frequency? Would a maximum usable frequency be involved? Thank you!