I ended up with a massive stash of mil-spec CDE Mica caps recently, and was searching for a refresher on decoding their military part numbers like “CM05FD221GP3”, since the caps came marked for their values but not their voltage ratings.

I stumbled on the Xtronics Wiki page about reading capacitor codes, which has all the info I needed, and more. It has instructions on reading EIA and Miiltary codes, and tables of the tolerance, delectric materials, temperature coefficients and ranges, and working voltage codes.

Turns out, those are 500V CDE Mica caps, 2%, and with a +/- 0.05%+0.1pF capacitance drift over temperature. Not bad!

If you need a quick reference for all these different codes, definitely check out the Xtronics wiki.