We don’t need the SKS, we have gun designers at home! In the early days of the Cold War, the Czechoslovak communist party was on very good terms with Josef Stalin, and were able to design and use their own small arms. A whole new slate of small arms were developed in the early 1950s, with a rifle, pistol, and light machine gun all adopted in 1952 as vz. (model) 52. The rifle used a short-stroke annular type gas piston that was located around the barrel. It was chambered for a proprietary Czech 7.62x45mm cartridge, as was the vz.52 light machine gun.
When Stalin died in 1953, the new leaders of the USSR were much less tolerant of Czech small arms independence. They allowed the country to continue to use non-standard arms, but required them to convert to the 7.62x39mm cartridge. This led to the vz.52/57 rifle, which went into production in 1957 and ceased production in September 1959, replaced by the vz.58. The only substantial change to the 52/57 was the chamber, and a slightly adapted magazine with a spacer in the front to better fit the shorter 39mm cartridge. The 52/57 magazines are recognizable by their flat floor plate, where the vz.52 magazine has an upward bend at the front of the floor plate.
A total of 99,475 vz.52/57 rifles were made, all at the CZ Uhersky Brod factory. Original vz.52 rifles were not converted to the 7.62x39mm pattern; they were all left intact. Both vz.52 and 52/57 rifles were distributed widely as military aid after the adoption of the vz.58. Many of them went to Cuba, and thence to many other places in central and south America.