Assuming 12 gauge, single trigger, beavertail, and matted rib, asking prices will be in the $4000-5000 range, with most candidates occupying the lower half of that range. If the seller is intent on moving the gun realtively soon, he might have to soften the price 10% or so. If the condition is bumped up to about 98%, the price could be as much as $1000 more. Condition is a real lever, depending on which side ot the trade you're on. Date of manufacture has little or no influence on price, but it seems that some of the very early guns with the "perch-belly" stocks and semi-pistol grips are real turkeys in the market place. Look around. There are always a lot of 21's for sale