This was in the trunk of my national when i bought it, don"t know if it works or not. Previous owner had already changed it to vacuum brakes. $245 with a free ride in the u.s. outside that we can work a deal if needed.
IMO - If it's found in a trunk, condition unkown then it's a core.
(Suppose you could install & test drive on a car to see if it's still good)
FYI - Kirbans currently giving $125 credit for complete cores.
Don't know if correct resevoir is required.
Believe there was mutiple resevoir variants on the powermaster though.