Coming back to the works bikes , I think people are confused with the term works racers,from the mid fifties the works nortons were on a very small shoe string and they developed things very slowly.for gods sake they did not have welding gear at the factory in bracebridge street,if anything required welding joe craig asked one of the mechanics to go home with a flat bed sidecar to pick up his private gas bottles,so much for no expense racing,and at some continental meetings they put the bikes in the guardsvan of a train and went that way.
Doug Hele when he took charge after Joe Craig left in 1955,only did small engine development on the Manx and the dommiracer twin,there was no new bikes every year trust me Amc held very tight purse strings "so ther was no new bikes every year.
All frame manufacture were by Renolds tubing where Ken Sprayson was working,they frames were made in small batches there was no special one offs for the factory
the only bike that had a lot of difference was the low boy dommiracer and I think they only made three of them in about 1960.the factory did alter some frames to put an oil reservoir in the frame for chain lube,and they did a couple of lowered head stocks to make the Manx height lower,and changed the brake system to 4 L/S
and the back hub changed to sprocket on one side and brake on the other.
Annealling the frames was standard practice on Moto Cross bikes,for the same reason as the racers
I remember Dave Hughes raced the old "Wheel barrow"Arter Matchless at Snetterton,when the frame came apart while he was on it,Peter Williams was apparently shocked to find that the bike was still been raced as he thought the frame was so light and only good for a few years only.He was told that the frame should have been annealed every now and then.