I came here looking for information on this. My cat is a short haired, ticked tabby. He has a very pronounced ridge down his back. It is a 1/2-1" in width of very shiny, solid black hairs, the hairs being about 3/4-1" long. It runs from just below his shoulders to the tip of his tail, tapering...
If I saw this cat outside, I would think it was mine and take it home. I've seen a good many of them around but few with the black, long haired ridge down the spine, as on your cat and mine. My vet said it's a common domestic cat (a bit of everything)