Early stuff was good. I’d look up what new stuff is going for and use that as a guide. If he has any sense, parting with something of high quality for too much less than new stuff that’s crap isn’t going to fly...and might be offensive.
If there’s rust or other wear, that may let you justify going lower, but if it’s been well kept....
As a side note, I HATE parasites who come by when moving, doing estate sales, etc. and think it’s okay to badly lowball on prices. Unless it’s an auction for insolvency, try to stay close to fair market value.