Rare WWII era Omega Triple Calendar Moonphase . All original . Sn 10827871 dated around 1943 Cal 381(27 DLPC ) 34.5 mm . ref 2471 1
https://forums.watchuseek.com/f29/omega-2471-triple-calendar-moonphase-4842645.html#/topics/4842645
https://www.chrono24.com/omega/cosmic-triple-calendar-moonphase-vintage-24711--id6521826.htm