My brake, clutch and throttle levers hava a chrome finish. As some other parts of this bike were chromed in the 60-ties, it could be that these were chromed too to civilise this bike. But the chrome on the levers looks different and seems of a better quality than the other chromed parts. So the question is: what finish did the levers have when they left the factory in '44?
The Advance / Retard is Matchless Bowden. The folded brake and clutch are 1950s or later ball-ended Doherty...I can't see anything there that is 'correct' for a wartime M20. The finish is probably not the most relevant aspect, but certainly bright chrome is not correct.
A choke should be necessary when cold and the handlebar set is not complete without it.