Item came out of South Africa so this particular shirt was likely used by SWAPO guerillas in Namibia. The cut is identical to Cuban Elm Leaf and Grey Lizard camouflage shirts but in herringbone twill material.
It was intended for export as seen by the English language “Made in Bulgaria” tag.
The two pin holes above left chest pocket (from point of view of wearer) could be from a safety pin for a political campaign type button.
Items in the camouflage pattern were likely exported worldwide to Eastern-Bloc aligned groups.