Type 64 Silenced Pistol
This integrally suppressed pistol was developed by the Chinese military during the early 1960s. Rather than adapt a standard pistol and add an external silencer/suppressor they incorporated the suppression system into the pistol’s receiver, giving it a bulbous, barrel heavy appearance. The Type 64 fires a unique rimless 7.65x7mm rounds and cannot chamber standard 7.65 ACP.
In addition to the pistol’s integral silencer the Type 64's breech slide can be locked into place, this prevents the extraction of the fired cartridge casing (which during a clandestine mission could be louder than the pistol's actual fire itself) and also minimised the sound of the slide recoiling. This mechanism turned the semi-automatic pistol into a single shot weapon. The Type 64 was supplemented by the less bulky Type 67 in 1968, however the Type 67 does not have the same slide locking system.
Jane’s Guns, Ian Hogg (1996)