Alvin, take a look on gunsinternational.com. Those are mostly dealers listing there, so if you find something similar to yours, deduct maybe 20% or so and that would likely be a decent starting point for a private seller. Right here, on the "for sale" section, would be a good place to list your gun.
If you didn't make a mistake listing either the chokes or barrel length, your gun is fairly unusual. Most of the 28" SKB's are M/F; the 26" guns are typically IC/M. With long barrels more in current favor than shorter ones, that'd be a plus for your gun. I'd list it here, asking maybe $1150. Good luck.
