Our friend Gabor Vass of Kaliber Info sent us this photo of a prototype flare pistol convention. The pistol is a Soviet SPSh-2 Flare Pistol converted to 9 mm R Knall (.38 blank ammo) + 28 mm rubber bullet.

The original SPSh Flare Pistol dates back to WWII and was invented by the Georgy Semyonovich Shpagin, who is better known for designing the  PPSh submachine gun.  It fired 26mm flares out of its 6″ barrel, making it well suited to 28mm rubber balls.