As far as I can tell, from watching prices on stuff being sold for years on the internet, what you do is take your old guns, add 20% to whatever the gun is now selling for new, and describe it as "LNIB, only without the box...a few scratches and some wear including the front sight broken off; no more than 5,000 rounds shot through the gun, lost the original grips so I glued a hot pad on the handle."