20mm Oerlikon Markings


Hey all

Got a round of 20mm Oerlikon the other day (Hstp (12,4,8)= 55,RG,OeZ) and posted the markings on the BOCN forum for ID. Here’s the BOCN thread
On the case wall just above the rebated portion there are the markings “SWN/262/56/HEI/TNT/N12Z” (and JohnMoss, those slash’s are part of the marking-I can see why it’s confusing)
Thanks to BOCN member ydnum303 for translating most of that for me:

55 = 1955 (year when case made)
RG = Radway Green (Ordnance Factory in Cheshire, where case made)
Oe = Oerlikon (the gun it was for)
SWN = Swynerton (filling factory)
262 = Lot number
56 = 1956 (Year filled)
HEI = High Explosive Incendiary
TNT = Explosive compound in shell

But as yet I have had no luck with the N12Z bit.
TonyE suggested N12Z could be Mk2Z but it is definitely N12Z (it is a definite 1 not l)
Could it be something to do with New Zealand e.g. When New Zealand purchased ships or equipment off the UK the ammo was part of the contract?



Is it possible that the marking may refer to the fuze for the projectile or is this marked on the fuze itself?



I never thought of fuze! I believe there was a BZ and KZ fuse. Was there an NZ fuse?