I am thinking of buying an Oris Big Crown day date 7500. The watch doesn't have any papers or box, no serial number on the back, and the original strap is also missing. I met the seller, who showed me the watch, so I took a couple of pics. First thing that made me suspicious is that the watch doesn't have the red rotor in it. However I kindly ask for your expertise in this issue.
Thank you in advance!