Can anyone explain the Kay vari tone system from the 1960s? I know the Silva Pro banjos had a cast tone ring, but there were also the 1000t 2000t and 3000t series banjos. Some of these banjos had a second screw in the heel ahead of the truss rod retaining screw. I gather this extra screw was for some sort of adjustment related to the vari tone system, can anyone elaborate? What does this extra screw do? Does its presence mean the banjo has a cast tone ring within? There was also a K90 produced from 66 to 68 and i have seen several of these that have the mystery second screw. I cannot seem to find any documentation online that lays out which of these higher end kays have tone rings and which do not, and how the vari tone systems works, and what the second screw in the heel is for.
I believe that only the 3 Kay Silva models,( K1000,K2000,K3000) had the Vari-tone tone ring, c.1956-59. In the 1960 Catalog, Kay had discontinued the Silva models, but kept the K1000 model number to describe their new top of the line banjo, which no longer had the Vari-tone tone ring. The extra screw in the heel manipulated a large metal shim that could alter the angle of the neck. Kay called this the Kay Kanti-lever.