Just a note, T-72A and M1 got composite armour on turret, T-72M was basically cast-turret T-72 upgraded to T-72A/M1 standard in FC, ammo storage, smoke grenade launchers and side skirts (and LRF).
For example Czechoslovakia had:
T-72 - original Soviet supply, optical RF
T-72 - Czechoslovakian production, LRF
T-72M - see above
T-72M1 - as M, with comp. armor
Of course, lately also T-72M4CZ
