The knobs probably changed in the late 60's and the later ones would have looked like this Jeff. This is off an SM465 that I was given, I don’t know what year for sure but I think it was a ’68 or ‘69.
http://www.pbase.com/dennygraham/image/112309889 The one we were originally talking about was the earlier one used on the SM420’s
http://www.pbase.com/dennygraham/image/112280998 . According to Novak the SM420 was used from ’47 to ’67 then in '68 they introduced the SM465 which was produced till '91.
I've been researching this and can’t find one spec of evidence that the embossed knob came with any trucks originally or were offered as a Genuine GM Accessory. The only way to know for sure is to have an original GM part number. I do think that some models of the SM 420 had the pattern embossed on the knob. We haven’t heard from any of the GMC guys about this, it just might be that some of the GMC’s had them.
I’m not positive but it’s a good bet that someone is reproducing them or modifying the original knobs. My nephew is a CNC programmer and I was going to ask him if he could program the pattern in on one of his machines and I’ll make up a simple fixture for the knobs. This would be a simple one evening project for any one with access to CNC equipment. I have a sneaking suspicion that is what we’re seeing here and that we will see more of these show up in the future.
Denny Graham
Sandwich, IL
