It's now my bike. Late 1915, 1916 spec 3 hp (425cc) twin. These Enfields weren't in use in WW1 (by UK anyway), other than very early by owners who took their own bikes. By 1915 all WD machines were in the supply chain. 6hp twins saw use as machine gun and ambulance units.
Still in it's original clothing, last on road in 1929.