Hi Stephen
Its a very late 1913/early 1914 3 1/2hp with the split timing cover, the later models had a one piece cover. The induction pipe looks correct. The cast alloy bend from the induction pipe to the carb and the carb itself is much later, the carb appears off a stationary engine and it appears that the motor has been used in that capacity, i.e. driving a saw bench or similar, as the solid flywheel has been reduced in diameter and a sizeable v-belt pulley fitted.
The 3 1/2 hp models were first shown at the Olympia Show of the latter half of 1913, underwent some redesign mid 1914 with regard to the oiling system,and the timing cover, the 3 speed gear box being then made available for sidecar equipped machines and by mid 1915 the model was superceded by the 4 hp model.
The Ladies model was only ever made as far as I known using the 2 3/4 hp engine.
Hope that is of some assistance
Regards SteveL
