I have shot one several times.
One of the best shooting SMGs I've fired.
The grip looks odd but feels good to the hand.
Can use Finnish Suomi mags.
Also shot a S&W M76. Preferred the Swedish K by a small margin.
Would take either if, I could get one.
Dillon's "The Blue Press" published an article on one several years ago.
It might be available in the archives.