Wondering if it is a Scarlet, pin, or black oak.

Never noticed any Fall color. Are they self fertile? Would planting a red oak near it cause it to make acorns?

Ask the oak what it identifies as :/

No other oaks around? Most any oak in the black group (black, scarlet, pin, northern red, etc) would pollinate it, IF the bloom period is similar. AFAIK, oaks sometimes produce a small number of acorns w/o pollination, but they prb'ly wouldn't be viable as seeds (the ultimate in inbreeding).

Some oaks are pretty stingy producing acorns, and you may just not have seen one of its rare "mast" years.

Oaks have both male and female flowers on each tree, but they don't self-pollinate very well. And they do hybridize, but not very readily, so planting a red oak next to your tree won't help much unless your tree is a red oak. Plant another oak of the same species as yours. But I can't tell what your tree is from that picture. My best guess is scarlet, but it could be pin. Could be red but I don't think so. Pictures of buds might help.

Oddly there aren't any oaks in the area that I know of, although on paper they should do great. The area used to be farmland, and the original developers planted mostly black pine and maple. The trees are mostly maple, locust, white pine, Norway Spruce, or trees with seeds delivered by small birds (eg. black cherry and eastern red cedar).

No branches I can readily reach, due to this incident. I had been considering planting a Scarlet x Willow Oak Hybrid (Quercus coccinea x phellos) or buying a Red Oak seedlings from the NH state nursery. Interested in Scarlet Oak, but can't find a local source that sells them other then in bulk. (And I'm running out of room for bundles of ten or more trees).

I'd be surprised if that tree is 40 years old. I think more toward 100 is realistic.

I saw an old picture showing the area was open fields in the 1920s. 91 years is the absolute oldest it could be. It's slightly smaller then the picture suggests.