This model refreshed Royal Enfield's model line-up for 1939.
It differed in cosmetic details, as well as in having two rocker boxes, which resulted in higher volumetric efficiency for the engine.
The numbers on the right side of the headstock are casting numbers (they stick out) and are not useful.
Numbers on the gearbox don't help with dating, but Graham finds them interesting if you can include them. I hope that Royal Enfield owners who contact him for help do so with the appropriate gratitude.
In 1933, a 250 cc option was also added to the range.