These grenades are manufactered by Plasticas Oramil of San Sebastian, Spain. They are generally produced as High Explosive grenades but, on order, smoke and incendiary fillings can be produced. All of them are thrown by hand.
The three grenades have the following common characteristics. Explosive charge: compressed Trilite Booster: Tetralite Firing arrangement: tape, striker and spring, inertia ball and detonating cap. Fuse: mechanical impact type Safety: a)Tape must be fully unwound. b) Inertia-ball prevents fuse functioning at ranges less than 7metres from the user. c) If the grenade is armed by the tape unwinding and it fails to explode, the fuse is left in a safe condition and the grenade can be lifted.
Model PO I
PO I : This grenade has a black bakelite casing and was used as an offensive grenade and acts very largely by blast effect. Maximum effect is obtained at 2metres and it is said to be effective at 3.5metres with a deterrent effect at 10metres radius. The impact fuze as described above is similar in function to the British No. 247 "always fuze".
PO III: Its normal application is in the offensive role, made of plastic, but it can be transformed into a defensive grenade by the addition of an external metal coil (see below). As an offensive weapon the shock wave is said to be effective at 3.9metres.