The TKB-506 Spy Pistol,

Created by Igor Stechkin in 1955 for KGB Cold War use, the TKB-506 was a pistol designed to be disguised as a cigar or cigarette case.  The pistol consisted of three internal barrels, each of which was loaded with a special 7.62 SP-2 cartridge.  The 7.62 SP-2 was a cartridge based off of the  7.62x39.  However the cartridge featured an internal piston situated up against the base of the bullet.  When fired the gunpowder charge pushed the piston forward, expelling the bullet.  The advantage of this system over a conventional cartridge was that the piston muffled the sound of the discharge, thus the 7.62 SP-2 was an internally silenced cartridge.

The TKB-506 was not meant as a combat weapon by any means, instead it was an assassination weapon through and through.  Silent and concealed, a KGB agent would whip it out, quickly put three bullets in a victim, then immediately vacate the area.  The original TKB-506 design came with a noticeable trigger, however a later model called the TKB-506A was also created which was smaller and lacked a trigger, using a button at the top of the pistol as a firing mechanism.  It is unknown how many of these pistols were produced, but the tenth in production is currently on display at the Tula Arms Museum in Russia.