1. $575 is reasonable if the gun is pristine, they highest I've seen a 357 mag over 20 sell for so far is $751.
2. If the grip cap is thin and groved, it should have a Savage medallion, but unfortunately, they were never glued on well, and tended to fall off with use.
First year, with the thicker squared off grip cap did not come with the medallion to my knowledge.
3. Plastic trigger guard is correct also.
