Omega Constellation Quadra - help before buy

Hi. Sorry for another post. I posted yesterday for advice before buying an Omega Constellation Quadra black dial with diamonds but the seller pulled out last minute due to sentimental reasons so the sales didn’t go through.

I have since found another constellation quadra. No diamond this time but has a mother of Pearl dial.

Would you guys mind having a look? There’s no serial number on the back… does this suggest possible counterfeit?

It doesn’t look fake to me, but I wanna just double check. The omega logo on the bracelet is also gone missing… the condition listed is ‘good’ (condition types: satisfactory, good, very good, brand new)

Thanks again!