These are original World War 2 armourers inspection rounds, used by armourers to source the causes of feed problems. These are coated in a material that can be scratched off. Armourers simply loaded one in a magazine and operated the bolt, after a close inspection the scratch would reveal the troublesome spot.
There is no head stamp but the sealed boxes are dated.
AUD$3.00 eachor AUD$115 for full unopened boxes of 48