In 1894 the Steyr company began making self-loading pistols produced from a design by Ferdinand Ritter von Mannlicher, a German living in Austria, who is better known today for his military rifle designs. Several models were made over the next few years, including the Model 1901 shown here. 
According to the Steyr factory records this weapon, patented in 1898, was originally introduced as the 'Model 1900' and used a special 8mm cartridge.
When introduced commercially in 1901 it was chambered for a special straight-case cartridge listed in Austria as '7.63mm Mannlicher', designated in Germany as '7.65mm Mannlicher', and described in the U.S. as '7.65 x 21mm'. The Mannlicher 'straight sided' cartridge actually has a slight taper to help in extraction.
The weapon's semi-automatic action is known as retarded, or 'hesitation' blowback. There was no positive locked-breech system. The rearward movement of the slide was mechanically retarded for a very brief period to ensure that the gas pressure in the barrel fell to a safe
level. The firing chamber and barrel in this design are fixed to the receiver. The magazine is housed in the grip and is loaded with a clip through the top of the open action. Because of the extremely simple lock work employed, the pistol has a minimum mass for this style of weapon.
The moving breechblock of this pistol was designed as a slide with two rails extending forward beneath the stationary receiver/barrel where they are connected by a cross beam which is also part of the single breechblock forging. The barrel is screwed into the chamber section of the receiver and has a front sight top rib which is part of the barrel forging.
A unique feature of this pistol model is the unloading device. While the breechblock is held open, pulling down on the serrated lever on the right side at the top of the grip panel will withdraw the lip which is holding the cartridges in the magazine, enabling the magazine spring to move the platform up and force all the cartridges out of the magazine.