17J vs 21J movements

[TQ]

I recently acquired a tired Sea Wolf, from the early 60s, and I'm trying to determine which version of the 70-72 movement would have been in it, originally. The inside of the case back is marked 722-916, which makes sense because the watch is a date model. The rotor, however, is marked 75 A. There must have been a rotor transplant at some point in the watch's past. What I want to know is, when did Zodiac install the 21 jewel 70-72, and when did they use the 17 jewel version? Do the 2 versions differ visually, from the rotor side? I assume that this movement is the 17j version, but that's only a guess.
Thanks,
TQ

[YuriyV]

Definitely, Zodiac 75 rotor belongs to GMT and is incorrect for this model (even it is the same part for whole caliber family, just marked to specific model).
Zodiac utilized 21J caliber variant for higher grade watches (chronometers, gold cased, costume watches etc). Usually those were nicely decorated and adjusted. Sea Wolf and GMT considered as a tool watches and used mainly 17j variants. But still were very good machines with nice aesthetic look and great performance.