I would definitely agree that Florigon is much more likely than Fairchild. However, as Squam points out, neither of thesse cultivars was extensively planted out back at the time this tree was planted. Doesn't mean it isn't one of them if the person planting it was "in the know" and a fruit collector/enthusiast or a person with someone that advised them who was. However, it could just as likely be a seedling and we'd never know without trying the fruit. Also, the Florigons, at least as my house, have begun to ripen and you see a fruit or two each day with a nice yellowish blush. I see none on this tree with any yellowing. Not conclusive, I know, but just another possible sign for consideration.
Harry