Well I can add a little here. I have a blank firing UZI that was made during this time period by a Japanese Company called Marushin. The gun operates as follows:
You disassemble the 9mm "plug fire" cartridges supplied with the gun and insert a special type of cap in the cartridges. The cartridges are then reassembled and loaded into the guns magazine. The gun should then fire in full auto as a rod in the barrel enters the tip of each cartridge when it cycles, hit the cap and set it off. This apparently works a lot better in theory than in practice as I've never been able to get my UZI to operate successfully.
I also had an MP 40 of similiar design that I never attempted to fire but I don't remember who made it. I sold that one off years ago to someone who wanted to use it in a display.
Jim
Thomas Jefferson, of Virginia:
"Laws that forbid the carrying of arms. . . disarm only those who are neither inclined nor determined to commit crimes. . . Such laws make things worse for the assaulted and better for the assailants; they serve rather to encourage than to prevent homicides, for an unarmed man may be attacked with greater confidence than an armed man."