The RAF Vocbulary of Stores was Air Publication AP 1086 . It provided a unique alpha/numerical identifier for every item in the RAF Inventory.
The first part, in this case, 12A is the Section the second part, in this case 876, is the Reference.
Section 12 covered explosive bombs and Section 12A was assigned to HE Bombs of all size and weights. But, so were associated bomb components and support equipment such as gauges for checking a Detonator holder. So the real clue is in the Reference Number.
I note that it is only four digits . Compare this to (for example) Clips, locking used on some marks of Tail Units for 250lb MC Bombs which is 12A/842
This does not mean that 12A/876 is for another type os Clips, locking although it could be. What is does suggest is it was assigned to an item of bomb hardware.
I note the plate has no holes for fixing or even a single hole for a tally yet it is engraved brass implying it was required to be sturdy to withstand repeated use. But, how would it be attached to a container. The adhesives of the day would have been ineffective.
I was an RAF Armament Fitter for 12 years from 1959 onwards and worked in bomb stores preparing practice bombs, HE bombs, Rockets and gun ammo. In some cases the HE bombs were WW2 stock dropped just to dispose of them but I cant recall seeing a similar plate to your query.
Returning to AP 1086, APs of the day, and indeed through the 60s, were loose pages perforated on a long edge and secured through very thick card covers. Two holes in each cover secured the pages with a 'shoelace' cord which went through from back to front. The free end of the cord was pulled tight and secured by winding it around a circular spring clip on the front cover. The ends of the cord terminated in a simple crimped brass ferrule. The reason for this was to enable amendment. Amendments to APs were frequent and varied from hand-written to replacement of complete pages. Most pubilcations were classified a minimun of RESTRICTED and removed pages were destroyed.
My point being, that with something as comprehensive as AP 1086 it is unlikely that there is a surviving copy of one that lists many of the Reference Numbers of a period of interest, indeed some References within a Section may have been reassigned.
I have flicked through a number of hard copy pages Armament APs which are in my collection but apart from the locking clips I mention above have not found a match for 12A/876.
