Gave even grand for standard grade 1 "twin-single", "horseshoe" forend", solid rib #27XX in May. Good deal better than 75% IMO. Looked hard at one from Tenn. dealer five years ago asking 1100$ which he got. They don't move up or down much. If you buy one (any Super no matter how many triggers) look to the bores as they'll rot in a heartbeat under plastic wad fouling. Reduced from factory length stock and the usual "Whiteline" is a 25% deduction according to Blue Book but I have yet to see anyone--dealer or private seller--who follows the formula when the gun's on the way out the door. Low serial number which your find has may also be worth something on the uptick. If it's tight and not abused, you won't get it for $800, to I'd guess somewhere in the 9-1200 range.
jack