OTs-01 Kobalt

The OC-01 Kobalt (, "Cobalt") is a Russian double-action 9 mm revolver designed by Igor Stechkin and Boris Avraamov.
The revolver was developed by CKIB SOO from 1991 to 1992 and was meant for sale to the Ministry of Internal Affairs and to law enforcement. In 1992 it was adopted by Ministry of the Interior of the Russian Federation as service weapon under designation RSA ("Revolver Stechkina-Avraamova"). Since 1994 it was also manufactured by "Zlatoust Machine-Building Plant" and "Uralsk Machine-Building Plant" under designation TKB-0216 ("ТКБ-0216").
Description.
The revolver resembles a Smith & Wesson "J"-frame revolver, with its small frame, "bird's head" grip and an external hammer. There is a safety on the left-hand side of the grip that locks the cylinder and hammer to prevent it from accidental discharge.
Since it fires rimless cartridges, the six-shot revolver is cut for "moon clips", sheet-metal holders that grasp the rounds by the base to allow them to be extracted easily.
The revolver uses a special Y-shaped "moon clip" that loads alternate chambers and locks into the other "moon clip". This allows alternating types of ammunition (like hollow point or armor-piercing) to be loaded into the same cylinder and allows the user to reload a special type of ammunition and keep the other type in reserve. It can also be used without the "moon clips", but the spent cases would not be extractable unless pushed out from the front of the cylinder with a rod-like object, like a pen or pencil.