I have two sets of the skirted S-76 knobs, the difference being the size of the skirt. One is 1-1/2 inches in diameter, the other 1-3/8 inches. I looks like the S-76 in the Dachis book has the 1-3/8 inch skirted knobs. Does anyone know why the difference? Did they change at some point during production? TNX es 73, Steve, K1WGN