Looks identical to our Toby when he was a baby.
He never developed the red markings on the side of his head, which led us to realize that he is not a red eared slider, but a closely related species.
My husband found him literally beneath the tire of his tractor trailer, at a truck stop, so if he'd moved it even a couple of inches, Toby would have been a goner.
As it is, he's growing quickly, and he now has a buddy, different species but almost identical in size, and they are getting along nicely. No idea of gender for either of them as yet.
Perhaps a River Cooter? They look somewhat similar, but no "red ears"