MiG-21PFM with the side number 7903 is one of twelve MiGs delivered to Poland in the 94N (nuclear weapons carrier) variant. Most of the time all machines of this version served in the 2nd PLM in Goleniów. After overhauls in the mid-1980s, they lost their functions as carriers of special weapons. Here I present it in an earlier period - with a gray cockpit and an IAB-500 bomb (these bombs were reportedly available only during exercises in Soviet units located in Poland).
Two sentences about the IAB-500 - it was a dummy bomb. Filled with almost a quarter of a ton of liquid fuel, it exploded creating a fireball about 100-120 meters in diameter for 3-4 seconds and then a cloud of smoke as high as 1 kilometer.