Random RF tube identification help

Hi folks! My father went SK two years ago and we're in the final stages of clearing out all his radio equipment. Amongst the detritus were 3 OTK-2 tubes. I'm guessing they're for high power RF amplification, but I don't have enough knowledge to identify them.

Markings on the tubes read:

ΓC Ι

96

83

1982 (guessing this is mf date?)

15

9

OTK-2

Pictures: https://imgur.com/a/kkmaIFN

Any leads on identification would be greatly appreciated. Thank you!