I find the CZ P.22, the CZ P.24, the CZ P.27, and the CZ P.38, but not the CZ P.28.
About the CZ 1927, my resource says: "...[M]arked the same as the CZ 1924, but the cocking grooves on the slide are cut vertically instead of sloped as on the earlier model."
Might you have a CZ P.24, made in 1938 (the last year of production)?
The problem with that, though, is that the P.24 was in 9mm Short (.380 ACP).
It seems that you have a nice little puzzle on your hands!