I just got this Omega Speedmaster Professional
I was wondering if any of you guys can authentic it by the pictures,

The watch seems original, but I'm unable to open the stubborn case back to check the movement, The watch works and so does the seconds hands but chronograph doesn't work.

So I just wanted peace of mind from the experts if you feel this is not the right forum for this please advise me on which one to try.

Where is the serial number located is it just inside on the movement or on the case also, as I wasn't able to see any serial number on the case.

I will be taking the watch to my watchmaker in the upcoming days to open it and then proceed with a service.