I have my doubt we ever manufactured wood for No 4 rifles. Possibly No 1 early WWII when we didn't have broomsticks to fight with. Terry would know the detail I believe.
I think the No 4 Mk II rifles were delivered late forties with spares.
If it is no 1 wood, when we could still buy a No 1 from government stores, we got spare wood with it. This didn't happen with No 4 rifles.
The new 'government' was horrified to realise soldiers could buy a rifle from government stores - arming the population as we didn't differentiate race in the sales, stopped it summarily and sold off all LE stuff, I believe at a give away price. Nowadays the 'government' would destroy all such and not sell it.