Yep, the Mk6 is a civilian semi-auto gun. Apparently, it was done by a “gunsmith.”
It surprised me when I found it jammed in there.I don't think it would even slip into place with that spring there.
That’s what I thought too, but I was wrong. I have seen the return springs put in wrong. The small spring inside the big spring and the cup against the endcap.
I thought this one was remarkable, so I posted the picture.
You two would enjoy the box guns. It’s a gun someone completely disassembled to clean, then couldn’t reassemble. All the individual parts are in a box. Hence the name. They have a way of showing up at cocktail parties when the owners know you are into guns.