Dragan provided the following extra information :
TKK, meaning "Trajal Korporacija Krusevac".
Factory is in the serbian city Kursevac and it produced smoke and chemical granades both in former Yugoslavia and now in Serbia.
Old name of factory was "Miloje Zakic" and the label on manufactured granades was MZK.
The name was changed to "Trajal Korporacija" in 1997.
Both grenades on the photos are manufactured in 2001 (TKK 0401) and in 2002 (TKK 0502).
The one produced in 2001 is for domestic use (all markings in cyrillic letters).
The one produced in 2002 is manufactured for export (all markings in latin letters)
The "m" is for modified, meaning the smoke mixture in grenade is changed for more "enviroment and manufacture safety".