The DUO was introduced in 1926 by F. Dusek, hence the alliteration in Dusek Duo. The one pictured is pre-war and has the Dusek name. Some were made for the Germans in WWII. IIRC, after the war, the communist government wanted to consolidate arms production and gave the Duo design to CZ, so it is under that name in some lists. Fjestad states that the pistol is still being made as the "Z" pistol by CZ, but I assume they cannot be imported because of the GCA 68 restrictions.
It is a very nice pistol, reasonably accurate and extremely reliable; it is one of the few .25 Autos I consider on a par with the old Colt and Browning.
Jim