20mm shell


#1

Question. I have a shell marked 20mm MK4 1944, slug marked 40-j-lo7, brass tip marked No. 2531-A.
A diamond shape stamp with rectangle on the end cap. Manufacture & any information ?


#2

Is there a small “B” inside the diamond?


#3

A picture would be helpful.


#4

Could be, looks like a solid rectangle with dent on right side.