I think it is RWRP too - there is a black dot. Mind you if someone changed the wire, who knows which way the screen and live are connected. You can check if it is reverse polarity by putting it over one of your other pickups (top to top). If they attract it is reverse, if they repel it is the same.
Not sure how you test the winding direction, other than wiring it in with another pickup. If it is RP, if you get the wiring right it will be hum cancelling and have a strong tone. If it is very weedy and out of phase, reverse the screen and core wires and try again.