The Czechoslovakian military adopted the vz.38 pistol as a simple blowback action chambered for .380 ACP (well, the Czech military version of .380 ACP). Other countries were interested in other calibers though, and the factory looked at making the gun in 9x19mm Parabellum as well. They first tried a simple blowback version, but that was not satisfactory. So next they developed a locked breech model using a rotating barrel locking system. It also had several other features beyond the Czech pattern; a DA/SA trigger and a manual safety. Two examples of rotating barrel guns were made (300001 and 300002) for testing. That was the end of the project, although I am not sure specifically what the problem with the design was (or if there just wasn't sufficient customer interest to justify further work). This is the only surviving example, as the other was destroyed during testing.

Many thanks to the VHU - the Czech Military History Institute - for giving me access to this unique prototype to film for you. The Army Museum Žižkov is a part of the Institute, and they have a 3-story museum full of cool exhibits open to the public in Prague. If you have a chance to visit, it's definitely worth the time! You can find all of their details (including their aviation and armor museums) here:

https://www.vhu.cz/en/english-summary/