Watchtower soldiers

This is the back of F73k_op1_ae2803_v079. Text with pencil: "Watchtower soldiers - 2/1 Field Batteries - 21st Artillery Regiment." Belasitsa Mountain. 17,5 x 12,6 cm. Bulgarian language. Paper.Dirty. Original reference: BOX3; F73k_op1_ae2803_r079.