When the Stemple STG-76 was designed, it used internal parts from the Finnish kp/31 Suomi submachine gun. Since the whole point of the Stemple was to have a modular and interchangeable gun, it would make sense for BRP to make a version that duplicated the Suomi as closely as possible. This is especially true given that the original Suomi is an excellent SMG with readily available magazines, but very rare to find in the US today.