The MS3 is a pressure-release mine or booby-trap similar in appearance to the PMN anti-personnel mine. It has been found in Afghanistan, Tajikistan and Ukraine. The bakelite lower half of the mine appears identical to the PMN but is reported to contain more explosive (I have not weighed it). The top is a black-rubber cover with a small raised cone in the centre.
It has the same firing pin and booster as the PMN.
Explosive charge: 310g TNT
The device is armed by removing a safety pin when a 5kg (or greater) weight has been placed on top of the pressure plate. When the weight is removed, the striker is released and the device functions.