These pickups fascinate me for a number of reasons. They are maligned and unwanted because they are not Pat. Pend. Humbuckers, and because everything Norlin is maligned and unwanted. These tarbacks must be rather rare, are they not? I know that MANY people in the 1970s were taking their tarbacks out of their SGs and Les Pauls and replacing them with DiMarzio Distortion. I myself thought of doing it but I never got around to bothering with it. Are these tarbacks rare? I suppose that the reason for the "tarbacking" was to give durability to the pup by "potting" it in an epoxy-like substance? The earlier Gibson Humbuckers were not potted. Were there some issues with them going microphonic? If so, Bill L. fixed that problem! Were the Les Paul and SG tarbacks the same pups or different?