Type C bombsight compass, which types was it used on ?.

I have seen many of the later type D bombsight compasses over the years, but only a couple of the earlier type C. Can any one please enlighten me as to which types of aircraft, the type C would have been used on etc.
I believe that the type D, was used from the mid 30’s onwards, so would guess at the type C being from the early 30’s.

Cheer’s.
Bob T.