This 6 kopeck commemorative stamp, issued by the Soviet Union in 1963, marks the 20th anniversary of the Treaty of Friendship, Mutual Assistance, and Postwar Cooperation between the USSR and Czechoslovakia. The design features the flags of both nations alongside symbolic cityscapes: Moscow’s Kremlin and Prague’s Hradčany Castle. The central background bears the emblems of the Soviet Union and Czechoslovakia, signifying their socialist unity. Rendered in shades of brown and red, it embodies the ideological alliance that defined Eastern Europe’s postwar order.