Rolex GMT 1675

The bezels are friction fit, no click spring or bearings- just a retention wire. They get cruddy very easily underneath and can get bound up- particularly if someone tried to grease it and that grease turns to tar.

The bezel will pry off easily with a case back tool (put a strip of electrical tape over it to not scratch the case) and clean it up with Naptha (lighter fluid) to remove any gunk or sticky residue. Reassemble and it should be much easier.

You should be able to turn the bezel smoothly with your fingers, but it should not be so loose that it moves around due to motion of the watch or minor incidental contact. It probably needs cleaning. The bezels have no particular issues that I'm aware of.

Value is highly dependent on condition and originality, so we would need comprehensive photos. People often provide a description that doesn't turn out to be quite accurate once photos are actually shared. For example, if any original parts were replaced during one of the times the watch was serviced, the value could be reduced by as much as 50%. Also, 1966 is a transitional period for the ref 1675, so we don't even know which variant you are talking about. TBH, it's more helpful to provide the serial number instead of claiming a particular year of production. So overall, based on what you've posted, I'd say the value is in the range $8k–$25k.

Well, it's hard to tell from that photo, but at first glance it doesn't appear to be a gilt-gloss dial, and also not the correct dial for an early matte 1675. So I would say that better photos and more information are definitely necessary to figure out what your friend actually has.

Nor does it have the original rivet bracelet so assume a later service replacement. Pictures of the clasp code would tell the year.