To make an authentication you need more info and of course more pictures (top, side, back, movement, case back, as much pictures, in highest resolution as possible). And I guess you know that already very well.
Where you got the watch from, is actually of no interest for authentication.
The watch always tells the authenticity itself by evidence.
First quick impression without in deep comparison: Dial very clean for the age - probably to clean. Central space of the dial with vertical texture maybe not correct. Crown maybe not correct.
Those steel calendars are often subject to fraudulent falsification.