CEKPETHO
There are a lot of "interesting" Russian military surplus capacitors, including PIO, Teflon, as well as more common mylar, and poly)
Sometimes the seller's description gives no indication of the cap's specifications other than simply capacitance and working voltage.
I've been doing a bit of research, (this is still a work in progress) and attempting to figure out this mysterious
"Sekret Kommie Kaps Kode" and I have some preliminary results:
(Note, some of the letter suffixes use Cyrillic letters, I can't print them here, I'll use the English equivalent for now)
K15-4 Ceramic HV "doorknobs"
K15-5 Ceramic HV Disc
K31 Silver Mica "kidney bean" style cap
K40P-2B Paper in Oil, 5% tol.
K40U-9V Paper In Oil , Silver body, 10% tol.
K41-1A PIO, High Voltage "Pulse" caps
K42U-2 PIO, green painted body (K75 are better)
K50 Aluminum Electrrolytic
K71-7V Polystyrol "High Tolerance" 1% or 2% tol.
K72P-6 Teflon Dielectric 5% tol. (see example below)
K73-14 PETP High Voltage
K73-15 PETP / Dry Mylar
K73-16 PETP / Dry mylar
K73P-4 "tub " style AC capacitors (may be paper or mylar, still TBD)
K74 HV caps
K75 Polyprop In Oil
K75-10 PIO, Green body (these are the prime quality PIO)
K75-15 PIO, High Voltage "tub"
K75-17 PIO High Voltage "tub"
K75-24 PIO Green body tubular (see example below)
K75-28 PIO High Voltage "tub"
BMT-2 Paper In Oil
FGT High Voltage Teflon Dielectric, Ceramic body (almost beer can size)
FT-1 Teflon Military Grade glass sealed, aluminum body (smallerst)
FT-2 Teflon Military Grade glass sealed, aluminum body
FT-3 Teflon Military Grade glass sealed, aluminum body (largest)
KBG PIO (no, this isn't the KGB, they're a different entity altogether)
KBI HV "doorknob" RF / Transmitting cap
KSO Silver-Mica "precision" caps
MBG Paper-Aluminum "tub" AC caps
The letters OTK are initials for "Otdyel Technicheskovo Kontrolya" Oтдел Техническово Контроля or Bureau of Technical Control, which indicates that special mil-spec or industrial testing standards are applied. In other words, "Top Shelf"
CEKPETHO
Oh, yeah, this means "Secret" in Russian, and in Cyrillic-looking letters Yellow_Light_Colorz_PDT_11
An example of the teflon dielectric, metal body, sealed glass capacitor,
0.1 uF, +/- 5%, 500V (this is a large cap, about the size and heft of a D cell battery)
A close-up of the marking on one of the K75 green PIO caps, this time they use European/English style, rather than Cyrillic letters)
[img]http://www.tonywelsh.com/images/K75-24_2[1].2uF_400V-nom.jpg[/img]
I've found LOTs more data to be triaged / munched and otherwise processed before posting.
A good reference site is here: http://www.luch.biz/lubitel1/eparts/