In the Royal Enfield US Community Forum we find this bike, a Royal Enfield WD/CO/B,
which does not have an Albion Gearbox. The reason for this is that the Albion factory was bombed in World War II and that slowed down production. Royal Enfield had an army contract and had to deliver the bikes so they used Burman gearboxes in about 3000 bikes. The Burman gearboxes were used in many other motorcycles (Vincent, Matchless). The location of the factory that supplied the gearboxes for the Enfields in 1942 still exists, fly there with live maps,
The Burman company continued in operation for many years, having been sold by the Burman family, it first moved to the old Ariel works in Grange Road, Selly Oak,
and then to the old BSA works in Montgommery Street, Sparkhill when it merged with Hi-Ton engineering.
The company went defunct in 2006!
To close, here is a WD/CO/B in action,