Box and flare with electric primer of Czech production.
headstamp is “irv 83”
What is it used for?
This one was used for perimeter security and border installations which were tripwire actuated.
They exist in different colors and loads (day / Night).
These also do exist in a variant where next to the original primer a hole was drilled and the bridge wire igniter (that cable you see) was inserted and sealed.
After communism had ended in Czechoslovakia and borders were “disarmed” such ammo became cheap surplus and many “inventive money savers” clipped off the cables and used the ammo in normal flare guns again.
Not to confuse these with the tear gas load and the “accoustic” (loud sound report) which were used for police vehicles in anti riot ops.
EOD, thank you very much for the information.