There just aren't a lot of possibilities for a mechanic w/ the initials >>C.F.<< with 3 possibilities:
Carl Fleischer - Mehlis
Christoph Funk - Suhl
C.A. Funk - Suhl
Now, I would sort or rule out Carl/Karl due to the use of the K for Karl up until a certain date that they began using C for Carl.... Too, I think it might be a Suhl mechanic so that would rule out Büchsenmacher Fleischer.....
Might you pleasure us w/ the full ensemble of marks, including both tubesets?? If you do now wish to deal with postin' images, you can forward them directly with me?
Serbus,
Raimey
rse