Pre war ES2 Norton and some dickhead sawed the magneto drive off. Can't see the forks but it appears to be a hint of long road holders. so it could be immediate post war although I didn't think Sturmy Archer gear boxes were still in use then. It could be a "bitza" Norton.
Could be broken. Either way its screwed. I had a '49 500T (trials engine) years ago. I used the cam cover from a '60 Model 50 (350) and a BTH magneto from an old Velo. Everything bolted together. The Model 50 was points ignition and used a distributor in place of the mag. The distributor bolt pattern was the same as the BTH mag bolt pattern. That was one of the beauties of the British. They kept things the same. The innards of that Sturmy Archer box are just about the same as a late AMC box.