There is a 28 two barrels set, both 26" 28 ga on gunbroker right now. Price 4725 with nine hour to go. I would rather have 28" than 26" but some go the other way. When the hammer falls I expect it to sell for 6-7 plus. It is pristine from the photos and most of the bidding for this type of set seems to happen in the last few minutes of the auction as one bidder or another try to swoop in and steal it.
Having a 28 / .410 set with 28" barrels should bring more than a 28 two barrel set. Do you have a for end for the .410 barrels set? You just do see them every day but one, with 26" barrels and two for ends was listed on Gunbroker again for months on end but never sold. It ranged from 11,500-12,500. Dealers seem to be willing to troll for a long time and then deal in person if a buyer has real money in hand which never gives you the selling price just the trolling price.
Back to your question a composed set with two for ends should be 7,500-8,000 range. I would not sell it for less unless I had a pressing need which I hope you never have. And if given the choice of 26" or 28" I pick 28" every time. But he market is what you get and if you get a buyer who wants is a lot you might get more.
