The original seat looks similar, mine had no tool box, mine had the upswept exhaust pipe, the pushrod cover was one piece, the girder forks on mine had been replaced with telescopic forks and the timing cover went up to the magneto which in itself was a pain due to water getting into it, the BSA logo on the tank was a separate item and not a transfer, the electrics were by Lucas the Prince of Darkness.
You could give me any screw from that bike and I could tell you where it went, I fitted a new small end and bushing, I worked in the tool room at that time so I borrowed an adjustable reamer to do the job. The silencer had rusted out inside a bit and it was too loud so I stuffed wire wool down it, at night my bike left a trail of sparks behind it, quite something to see.