During WW1, as trench warfare intensified and the need for fast-firing close quarters weapons grew, there were many experiments with converting semi-automatic weapons into fully automatic light assault weapons.
One weapon that saw such conversions was the Hungarian Frommer Stop pistol. The 1912 model Frommer existed as a special assault variation with a longer barrel, extended 15-round magazine and a fire control switch for allowing fully automatic fire - this model being called the Frommer M.17. Like many other pistols used as assault weapons, the Frommer would also be equipped with a wooden shoulder stock for increased control.
When the Austro-Hungarians came up against the Italian double-barrelled Villar Perosa submachine gun, they were very impressed with the terrific rate of fire, and they wanted a similar weapon of their own.
This led to the Frommer M.17 being developed into a dual submachine gun which was essentially two fully automatic Frommer M.17 Pistols with modified triggers, put upside down in a special light tripod mount and each having a 25-round box magazine. A small series was made and deployed on the Italian Front.