Is that Norton in a Trackmaster frame or maybe Sonic weld ? For some reason it doesn't look like stock Norton
I think this is a stock frame with Z plates and Isolastic... a Trackmaster would not any of that. I tried to compare with the one on mine, through pics, and I cannot find any notable differences. Ok on my pic I replaced the Z plates by something “lighter”... another give away is the knob on the shock mount to pull the seat off.
Stock frame. The bike was built by Bill Bibbiani aka: "Bib". Bib was the head of the Southern California Norton Owners Club and when he passed away back in 2013 my friend Jeff bought the bike from his widow. The sticker on the rear fender is for "Bib". Sorry again for the digression so here is a Sidehack pic: