I'm used to seeing a cast B&O capital dome centered on the smokebox door, so I was thinking PRR with a circular plate in the same spot, but then the low headlight mounted on the pilot is wrong for that. Perhaps it's B&O and someone liberated its smokebox door casting or it was one without it? Perhaps it's all been modified for use on a shortline? I couldn't match those circular handrails exactly. It has an air tank mounted high on the boiler, so that may also be a clue.