If you hold the trigger down, it can be fired in full automatic. Alternate fire is semi-automatic fire.
This pistol can be dual-wielded thus increasing fire rate and killing time.
When "if best" is switched on, the Mauser Pistol ranks as the 8th worst weapon on TS1, on the same level as the Pistol, however its dual-wield variant is 19th best weapon, on the same level as the Pistol (x2).
It is possible that this was replaced by the Luger Pistol and Kruger 9mm in later incarnations of the game, although they are based on an entirely different weapon.