If corvus' dog views something as P+, its P+. Whether something is punishment or reward is defined after the fact, by the dog.... by noting whether or not behaviour DID increase/decrease.
IMO, a choke collar is usually P+. A PRONG is R-. A choke is applied by the trainer to punish the dog. Classic P+ (provided it works of course).
The prong tightens while the dog is pulling and the pressure/discomfort stops when the dog stops pulling. I think R- is the hardest one to get your head round and the hardest one to display examples of. In the case of Skinners box, I think rats received electric shocks through the floor until they pressed the lever and then the shocks stopped.
If you were to use a choke incorrectly - ie, dog pulls, dog chokes, dog stops pulling, pressure/discomfort is released, then yes, its R-... but that doesn't usually work and is incredibly mean to the dog. If you were to leash pop a dog with a prong collar then that would be P+, but I don't like them being used that way.