Fast forward nearly six years since I posted in this thread "When I was young, an elderly woman told me the names of the varieties of the two apple trees in the backyard of their farmhouse. Those trees are both still alive. One is on the Central Wisconsin Apple Rediscovery Project list. The current owner won't let me collect a bud from it. Hopefully the tree is still alive after the current owner is no longer the owner, and hopefully I am still alive to ask the next owner for a bud. Since I'm not one to sneak over there and collect a scion when the owner is away, there is a note in my file where I keep my Will explaining to my descendants what do to in case I'm not still around once access to the tree becomes legally possible."
Well, I have ended up outliving the owner and, as fate may have it, now own the farmhouse myself and its ancient apple trees. The tree I'm looking for is one of three in the backyard that have huge trunks. All three trunks are full of rot, but the trees are still producing on the sides where the bark is good. I closed on the purchase of the property after the apples had already fallen. The clues I have to go on next year are (1) the taste description from the elderly lady long ago who told me it tastes "sour", which could also mean "very acidic", because she loved to make apple pies and (2) a written description that it resembles Duchess but is redder, weighs around 5-6 ounces, and is a mid to late season apple. We'll see if I can perhaps crack this mystery.