Hi,
It's been many years since I have looked at the VIN on a Norton, and more since I owned one (the last was a '67 Atlas), so this info may not be 100% accurate, but I hope it helps.
The VIN is situated on the left side rear fillet plate that the engine/gearbox plates bolt to, just below and in line with the uppermost bolt hole reading vertically from the top down.
The photo you posted has a shaded area in this position which I think is the VIN on that frame; your frame should have the number in or about the same location.
It should start with two digits (model code), one letter (year of manufacture), and five or six digits (number in series).
Expect some irregularity in these, as they were stamped by hand.
The Norton owners club, one of the specialist dealers or the Vintage Motorcycle Club should be able to tell you the year, model and possibly even the dealer who sold the machine.
The flat indentation on the inside of the right upper frame tube is to allow clearance for the rockerbox of the sigle cyl. engines, so the frame in the photo (and your frame also) is from one of these, likely an ES2.
The twins did not have this indentation.
I wish you the best of luck with your project.
A.
