We found this tree growing in a WWI era orchard on a south-facing slope at about 5000'. Off the tree it was a bit tart, but after two weeks in unrefrigerated storage it developed a nice tropical taste and had a nice crunch. After four weeks it was still firm, but the taste was getting blandly sweet with a hint of spice.
The smaller photos of the sliced apple were taken a month after picking, and the apple has yellowed quite a bit. The brown spot on the sliced apple is a bruise (whoops). It has a pretty nice aroma and kept as well as any in our warm basement about a month.
Any guesses on ID?