Zásahová výbuška P1
This anti-riot grenade is used by the Czech police and Army , and holds 14 "bangs" in 3 different delays of explosion.
5 x 0,8 sec / 5 x 1,5 sec / 4 x 2,2 sec, which together resembles fire from a machinegun.
There appears to be two types, a 130dB and a 150dB.

Length w/fuze : 127mm
Length w/o fuze :
Diameter : 50,5mm
Weight : 195gram
Filling :
14 pellets
Fuze :
TZ M3 or mousetrap-lever fuze (as on photos)

Information thanks to Milan.

The photo on the right shows the latest variation.

Below two photos of another manufacturer.

Pictures thanks to Milan :