This Swiss Mehrzweckwerfer 73/91 is a K-31 bolt-action infantry rifle cut down and fitted for a launching cup with an adjustable range. Instead of live 7.5x55mm GP11 ammunition, launching blanks would be loaded instead, and then you would insert a teargas grenade or a 'baton' payload. It functions exactly like WW1 and WW2 era infantry grenade launchers, but made for less-lethal munitions for riot control.
The baton load is a stack of short rubber hexagonal rods sitting on a plastic or fiber plate, which are packed together with aluminum foil or tight plastic, coming out at as a wide rubber shot spread. Switzerland has a LOT of K31 rifles around, so they're very cheap still, thus rebuilding a small fleet of old rifles (which may have had shot out bores for all one knows) to launchers is easy and inexpensive, and they'll last forever, they still use these.
I recall seeing some images of these with a special stock that bows downward so as to clear helmets and gasmasks when aimed from the shoulder (painted either black or teal), but now I can't find any which aren't ant sized.
For further information about these, this article is quite good and has many detailed images:
https://armamentresearch.com/the-swiss-mzw04-multipurpose-launcher/ 