Complex sentence: The first prototype watches were made in 1954 and were marked'Spartak', the'PRIM' brand was registered in 1956, the serial production started in 1957, thus Czechoslovakia has become one of only twelve countries in the world capable of producing wrist watches.
Split into simpler sentences: The first prototype watches were made in 1954 and were marked'Spartak', the'PRIM' brand was registered in 1956. Serial production started in 1957, thus Czechoslovakia has become one of only twelve countries in the world capable of producing wrist watches.