Sounds like fun guys....
---------- Post added at 02:14 PM ---------- Previous post was at 02:05 PM ----------
Many thanks for the pics, proving beyond doubt that the flaps saw service in the early part of WW2 at the least.
It's reasonable to hypothesise in that case, that these were already attached to WW1 dated rifles, withdrawn from stores, or, perhaps more likely, older rifles allocated to War mobilised TA units in 1939.