I think if Murray gets a bright light and a magnifying glass he might read "New Hudson" on the tank.
New Hudson went in heavily for the enclosed look in the early 1930s (lots of pressed metal enclosing the lower half of the motor and gearbox) so I suspect this example is from the late 1920s. Probably a side valve 500 from about 1929?
It's a handsome bike - a pity about the antiquated carbide lighting set!
Cheers
Leon