The SMART was conceived as a two-in-one weapon that would double as an infantry submachine gun and an anti-tank weapon, and was designed for the Bundeswehr's submachine gun trials. The blueprints were drawn up by a third party who commissioned Erma to produce the prototypes. The weapon was then submitted for testing at Meppen, where it performed well in both of its intended roles. However, it was rejected on account of its high cost. Erma dropped the SMART in favor of a cheaper design, the MP58.
The SMART was a blowback-operated 9×19mm submachine gun built to a high standard, and featured wooden furniture, tangent sights, and a perforated barrel. It could launch anti-tank grenades from the end of its barrel, and could be fitted with an adjustable 100m leaf sight for aiming the grenades. The grenades were launched entirely by gas pressure, so the SMART could be adjusted to fire from a closed bolt when loaded with a grenade. Otherwise, it fed from MP40 magazines.