Heres another of these watches that has a small movement - possibly "Banker" ?? 10kt RGP
Movement is labelled M9 and the case has N0 so have put down the case date.
Case is 21mm wide by 31mm not including lugs or crown. Lug end to lug end is 38mm
Edit: Same case as the 1967 Banker except for the little opposed bars stamped into the ribbing top and bottom