I have been looking into that rating you posted. I am stumped.
Very strange marking. I have not found anything that explains it, anywhere
Ii have looked.
.
The "cm" is the oddball thing.
Now if it was in PFD/MMFD/NFD it would be easily convertible.
(If they really meant pfd, it would be 1F, which is a lot of capacitance for a radio, especially in 1938, that would have been the size of a few rooms in a house!)
Its 1KV rating means its likely across the output transformer winding, correct?
Typically, I have seen them in the .01 to .008 mfd range used in that fashion, and up to 2KV rating, depending on the B+.