The Viper Mk I was an experimental submachine gun developed in the UK for use by military policemen in post-WW@ occupation West Germany. It was a simplified Sten gun (full-auto only, without the semiauto option normally included in the Sten trigger mechanism) put into a wooden housing.
It was intended to be carried slung over one shouldered fired under the arm with just one hand. To this end, it had neither sights nor trigger guard. The whole concept seems pretty questionable, and while multiple different Viper submachine guns were designed to fill this role, none were ever adopted.
Ian’s video [9:54]
That picture reminds me of Nerf blasters more than actual guns.
Clamshell cover for the looks, tiny bit of actual mechanism…
Both the P90 and F2000 are surprisingly empty clamshells as well if you want to look up videos or diagrams.