When I felt Tumble's backside on admission and noted a lack of male equipment, I assumed Tumble was a girl. But something about her/his unabashed friendliness and the shape of her/his face indicated "boy." She/he had a small wound under the tail, so I wasn't sure if we had a girl who had a prolapse, or a boy with an unhealed neuter. And Tumble was so friendly he kept spinning around to see what the heck I was looking at. So we let the vet decide.
Verdict: Tumble is a newly neutered male, with some scrotal tissue poking out of the incision, which they took care of. Since he was friendly, I foisted him back off on Nancy, who had rescued him (a highly experience fosterer for a variety of animal rescue organizations), and she is taking photos and reporting him as found, so hopefully we can locate his owner. Unfortunately, there was no microchip. He was likely hit by a car (or jumped out?) so he is one lucky kitty.
He is FIV/FeLV negative, a bit talky, and extremely friendly. He seems OK with Jack, Nancy's dog, but obviously has not been exposed to ceiling fans! "Whoa, what is that scary thing?" If we don't locate his owner, he will be up for adoption. Perhaps Felyne will come visit him when she comes East (unfortunately we are pretty far from Pittsburgh!).
Thank you also for Nancy for generously donating to the vet fund to cover his care.