Based on Gunbroker listings I've seen, the price difference between 1s and 3s in that condition ain't that much, even though the 1s are much, much nicer. The 3s do make up into a very nice custom.
If it's a Number 1, $800 or $900 would be much more than he'd get selling to a dealer. $1000-$1300, depending on wood, would be a typical GB price. If you offer him $900, he'd have no reason to think you're trying to skin him.
