I recently was sorting through a bunch of low end stuff picking out what I needed. I always run a magnet over the dupes before I place then in the “black hole” of my duplicate bin. You never know what you might find. In this case the magnet picked up an unheadstamped 4mm Ubungsmuition M.20. Upon checking, none of my other 4mm Ubungsmuition take a magnet. I assume this one has an iron anvil.
I know this is a rather plain and mundane cartridge but I have a few questions. Who made the iron anvil version and when? Does anyone have a picture of a cross section of this cartridge (with either an iron or brass anvil)?