My boss is looking to sell one of these - bought in the 80's, barely used.

Apparently the selling price is varied $300 - $600 online.  He was offered $100 at a LGS

Selling prices seem high to me - is there something about this gun I don't know?

Any ideas on what he should expect for this gun?

He was offered $300 "sight unseen" - I told him he should probably take it - but it seems like he could get more if he wants to put the effort in?

Thanks in advance!