I don't think the new dipping has hurt resale value. I haven't seen a New dipped one that looks anything like the originals. Anyone that wants an original probably wouldn't settle for a fake one and anyone that would be satisfied with the new dipping probably wouldn't pay the high prices anyway. You'd be better off waiting until Feb-March to try and sell one. Most people don't remember what a turkey looks like in the summer.
That tree bark one you have is an even more rare shotgun if it was an 870 I'd be making an offer.