Time to put the one I posted to rest.
Its a Filialen "Babygun".
Essentially a downsized Sten MK.II for concealed carry, it was basically a futher development of the Holger Danske "Fossgun":
Build either from the ground up, or at a period using shortened barrels from Suomi SMG's stolen from the danish police (Danish cops often aided the Resistance), they where easilly carried under a coat or in a bag or briefcase, and where rather succesfull PDW's.
Seen here is a Filialen worker testing both a homebrewed Sten MK.II and a Babygun.
The Danes made many Sten versions, below is a British Sten MK.II (top) and a long barreled "Ringen" (bottom).
This just goes to show you, you cant hold people down, even when they have no guns, they will just make them!
Courtesy of a friend on another forum.