The top flare pistol is the USA M-9 and the bottom is the M-8. They shoot the rimmed 37mm. The 8" flares look to be rimless from the photo and would fit the M-2 flare pistol as well as a few others manufactured by the same Co. " International Flare Signal Co. in Tippecanoe City, Oh ".
The rimless shells are inserted into the front end of the M-2 and are held in place by a side locking mechanism. This method is called the Driggs Faber system