The Frommer series of automatic pistols were the work of Rudolph Frommer, an engineer born in Budapest in 1868. At age 28, he was hired by the arms company Fegyvergyar where he began a very respectable career. He was promoted to general manager of the factory in 1906, and by his death in 1936 (having worked at Fegyvergyar for 40 years) he had more than 100 patents in his name.
His work on pistols focused on the long-recoil action. In most handgun designs the action is locked only long enough to allow pressure to drop to a safe level – the barrel recoils back a few millimeters before unlocking from the bolt (this is known as a short-recoil action). Frommer’s design, however, kept the breech locked throughout the recoil sequence, separating only after the bolt had reached fully rearward travel. This type of action (more commonly seen in the Browning A5 shotgun and Remington Model 8 and 81 rifles) spreads out the recoil impulse, but tends to be more complex to manufacture.
Frommer’s first pistol design was the Model 1901, which reached market in 1903 and was not successful (only about 200 were made). It was submitted to several military trials, but did not win any of them. It had a 10-round blind magazine fed from the top by stripper clips, and was chambered for the 7.65mm, 8mm, and 9mm cartridges.
The next iteration was the Model 1906. The first few 1906 pistols retained the early 10-round blind magazine, but the design was soon revised to use a more modern but smaller capacity 8-round removable magazine (which would serve as the model for the Luger P08 magazine). The Model 1906 was chambered for a proprietary cartridge, the 7.65 Frommer. This model is also very rare, with only about 800 made. They were tested by the Austrian military, but lost out to the Roth-Steyr (which would be made in the same factory where Frommer worked).
The third, and most successful variant to date was the Model 1910. This Frommer used the same long-recoil action and proprietary cartridge as its predecessors, but had a number of modernizations. The spur hammer was replaced with a rounded one, and the manual safety was replaced with a grip safety. It was used by the Hungarian police, and many more were made than the previous models (although still fewer than 10,000 in all).
Finally, Frommer hit the big time (relatively speaking) in 1912 with the introduction of the Frommer Stop pistol. While still using the same basic mechanism, the Stop was redesigned to a much more conventional look and chambered for the commonly available .32ACP (and later .380ACP) cartridge. It was still a very complex and expensive gun to manufacture, but it remained in production until 1929.
US Patent #802,279 (R.Frommer, Firearm, October 17, 1905)
Ed Buffaloe has a very thorough article on the Frommer pistols (particularly the Stop) published at unblinkingeye.com – and in addition to being very informative, it is also where we found the photos used on this page.