Almost all depts, HL, rotate their inventory through a local dealer, who advance credit on the tradeins against the cost of new weaponry. Let your fingers do the walking, calling all the dealers around and asking if they have many used 870s. When you find a shop with lots of these, Eureka!
The dinged exteriors will keep lots of folks from buying them, the shop has little invested, and until they get down to just a few left, prices will be great. One still can get a turnin for as little as $155 on occasion, tho $200 is more common.
Unless you pick the agency trainer, chances are it's had less than 100 rounds through it. Dinged finishes can be upgraded with Parkerizing, paint, slick treatments like the Robar stuff, or just lived with.
HTH....