WW2 Royal Ordnance Factory 20 munitions workers badge

A scarce original wartime period 'Royal Ordnance Factory 20 munitions brass badge with additional black and red painted finish, the reverse impressed with maker's details 'T.L.M. Ltd B'Ham' and official issue number '4933'. Good condition, complete with original pin fittings, replacement pin.
Diameter 31mm.

Royal Ordnance Factory with numbers were introduced from the middle of 1940, but their issue was ceased around 1942 because of metal shortages.