Some data here
http://www.franzitegrips.com/cz-duo.htmlFrantisek Dusek, born in 1876, established himself as a gunsmith in the town of Opocno in 1908. Interestingly, he refused to manufacture weapons or parts for the Austro-Hungarians during World War I, and he likewise refused to coöperate with the Nazi occupation during World War II. After World War I, he made rifles, shotguns, air rifles, and gunsmith supplies. He bought some unfinished pistols from the Praga Zbrojovka company when it went out of business in 1926, and finished and sold them under the Praga name. Then he began to import Spanish pistols under the trade names Singer and Ydeal. Around 1934 or 1935 he probably began to manufacture barrels for the Mars pistols made by the Posumavska Factory, and by 1935 he was selling .25 caliber Mars pistols with the Mars name removed and the slides marked ‘Automat Pistole “DUO”,’ which was an abbreviation of “Dusek, Opocno.”
CZUB "Z" Pistol, 1954Finally, in 1937, Dusek began to manufacture a .25 caliber pistol (a copy of the MARS, which in turn was nearly identical to the Slavia) based on the Browning design, but with no grip safety. Due to the Spanish Civil War, he was no longer able to import Spanish-made pistols, but because his customers were familiar with the trade names used by the Spanish, Dusek’s first pistols bore the name Singer, and later Ydeal. However, by 1938, he was using the name DUO.
Some of the DUOs sold in Germany were marked with the distributor’s name, Eblen. AND MORE .....
Mike