I have an old apple tree I need to ID. It's been untrimmed for years out in a horse pasture area that I plan on reworking into a new orchard area.

What do I need to note other than taking some photos of the tree? It isn't even budding yet. I have eaten a couple- they are about the size of small tennis/baseball? Might be bigger if the tree was pruned up. Red skin. Kind of tart. A more crispy flesh than mealy flesh. Not the best fresh eating though decent, but great when I baked it up with other apples, and for slicing grinding down into dehydrating. A dryer flesh rather than a juicy flesh.