The pickups vary by the Stringmaster model. The Stringmasters with the chrome covers are different than the later ones with the black plastic covers. The chrome covered ones are smaller pickups and wired together without a blend control. They are wound to about 6.7k ohms. The black plastic ones are wired differently with a blend control. They are larger, hotter pickup and wound to about 12K ohms.
I needed a couple of pickups for a Stringmaster I am working on and Jason Lollar whipped me up a couple, very nice!
Erv