The SM-9 was an American-designed, Guatemalan-produced submachine gun.
The SM-9 was developed around 1977, but the design process of the weapon is not well-documented. It was originally produced covertly in Guatemala by a company owned by CIA contractor James P. Atwood, overseen by Vito Cellini, an adviser to the Somoza regime. According to some reports, the gun was circulated among right-wing drug cartels, including the Contra movement. It is not known when its production in Guatemala ended, nor how many were made during this period.
Production of the SM-9 moved to the US in the 1980s, and it was rebranded as the "SM-90 Phantom". The patent for the gun was ascribed to Preston A. Edward in 1984, whereas the muzzle brake was separately patented by Vito Cellini a year earlier. The production rights were held by Wildfire Munitions Inc., the company under which the gun was marketed, although it seems that it was actually produced at Combat Military Ordnance Ltd., a company based in Savannah, Georgia which was operated by James Atwood and Kenneth Dunn. CMO Ltd., trading as Merex, were implicated in the 1985 Iran-Contra affair, and had been identified as one of the companies supplying the Contra rebels in Nicaragua.
The SM-9 is a blowback-operated submachine gun chambered in 9×19mm Parabellum. The weapon appears to have been developed from the International Ordnance MP-2 and as such is quite similar in terms of design both mechanically and in appearance. The SM-9 employs the use of twin sears, with one connected to the trigger and the other the front pistol grip; pulling the trigger gives single shots while holding the front sear and pulling the trigger allows for fully automatic fire. The front grip can be rotated to either side. Advertisements of the SM-9 claim that the weapon "exemplifies state-of-the-art technology and computer-controlled manufacturing to provide one with performance and precision never before offered in a lightweight, compact automatic assault weapon", although this is likely a cover to disguise the weapon's true nature.