Looks like a pretty nice set of signs for sale this year
www.friendsofbaxter.org
The one sign they have never auctioned is the one at the end of the AT at the summit. I think the AT museum in PA has a retired one and would guess that the new MATC trail crew facility may end up with one if and when it gets built. Maine Appalachian Trail Club destroys all their old signs as they feel it would encourage theft if there was a market.
I havent seem if AMC is having their annual auction yet, but in recent year the selections tended to be more obscure locations with a couple of high visibility ones to keep up the bidding. RMC now auctions theirs in the spring.

The annual Sign Auction is open for bidding. — Friends of Baxter State Park
Our Friends of Baxter State Park sign auction is a chance for you to bring home a part of your favorite place, Baxter State Park. Each year, we collect retired Park signs some of you may have seen on one of your own trips!
The one sign they have never auctioned is the one at the end of the AT at the summit. I think the AT museum in PA has a retired one and would guess that the new MATC trail crew facility may end up with one if and when it gets built. Maine Appalachian Trail Club destroys all their old signs as they feel it would encourage theft if there was a market.
I havent seem if AMC is having their annual auction yet, but in recent year the selections tended to be more obscure locations with a couple of high visibility ones to keep up the bidding. RMC now auctions theirs in the spring.