A shop a few miles from me had a 6" barrel .22 Officers model for $600.

Good deal? Too much?

It is in about 95% condition and locks up very tightly.

It has the silver medallion Colt grips which are in nice shape also.

TIA!

Depends on what era of Officer's Model.
Is it a pre-war Officer's Model Target, or a post-war Officer's Model Match?

That price would be about fair for a .22 in nice condition.  
These were specifically built to be formal Target Match revolvers. Up until the Python, the OM was Colt's top-of-the-line DA revolver.
When in good shape, proper timing, and adjustment, these will almost always out shoot any other DA .22 ever made.

Seems to be the going rate around here.  Not the easiest thing to find.