The October Revolution in 1917 ended the Romanov dynasty after a 300 year period of time.
The Bolsheviks led by Vladimir Lenin overthrew the Russian Provisional Government which had replaced Tsar Nicholas II. After Lenin's death in 1924 Joseph Stalin came to power. Stalin initiated a centrally planned economy and as a result the country was forced into a rapid industrialization and collectivization. Stalin removed his opponents from the Communist Party through arbitrary arrests and persecutions of many people.
After Germany invaded the Soviet Union in 1941the Red Army defeated the German army in 1943 in the battle of Kursk and finally shattered the German forces in late '44.The territories overtaken by the Red Army became satellite states of the USSR. This was the start of the cold war starting in 1947 and ended after the collaps of the Soviet Union in 1991.
A lot of watches from that era in time are commemorate examples. A view of these examples can be seen on this website.