Found this on the web.....
"The small, pocket-sized Vz.50 was developed during late 1940s for police use and it was chambered for the marginally powerful 7.65x17 Browning ammunition. Apparently influenced by the Walther PP in design, the Vz.50 had several differences in safety and disassembly. In the early 1970s the basic design went through minor face-lift, and the “new” design received the designation of Vz.70. Many Vz.50 pistols were refurbished to Vz.70 standard, with different finish, grip panels and a slightly different safety lever. New Vz.70 pistols were also manufactured between 1970 and 1983. After the replacement in service of the older Vz.50 and Vz.70 by more modern 9mm Vz.82 pistol, most were sold as surplus, as Cz-50 and Cz-70, respectively."