It seems configurations of these were not very consistent it's therefore difficult (impossible ?) to be strongly positive about authenticity
Checking every crucial parts instead sounds like an acceptable process to me
As Georgieboy58 said, plexi looks like a replacement, here's what the loupe should look like
I can't see well the bezel but it would maybe deserve a clean photo to fully check
on the other hand, we have
what looks like a nice case, case back showing some refs and serial, correct big crown, nice dial with superb lume patina, correct H/M hands (that deserve a professional relume though), the sweep hand could be correct as well, the bracelet is a strong plus to me if the clasp is correct
Drawing a final conclusion is something personal, the key issue is to be aware of what we're about to get
Hope it helps
Best,
Laurent