Material: cotton khaki “diagonal”, specially made for copies of the Soviet uniform, a very good copy of the original fabric. Not a "glass", not a synthetic modern fabric! The correct color and texture! High-quality tailoring.
Second-hand item (used earlier).
We have only one shirt, size 48-50. The width of the shirt at the waist is always larger than the shoulders, it is sewn like a loose shirt, like a "bell". Measures for this particular item in the image below.
"Gymnastiorka" (literally: gymnastics shirt) model 1935 was used in RKKA from during the war till 1943, when a new model uniform was adopted. After that it had been used with shoulder boards untill stockpiles were depleted.