Picked up a couple of weeks ago was the dummy at the top of the picture. I suspect it to be a 7,92x75 BESA but there is no headstamp. I base my premise on the dimensions of the round. The pocket is blind with a round topped central anvil. The case is drilled in 4 places and there is a red stained wooden distance piece visible through the holes.
The case measures 56mm in length and has marks on it that indicate that for part of its life it was in a linked belt. The bullet is grubby and slightly magnetic.
Is it British? Is it a BESA?
Happy collecting, Peter