I think this Union pull-chain design, a very competent copy of a Huret from the 1950s, is the earliest of the Czech derailleurs in this collection. It is clearly a close relative of the Favorit (1st style), but the black finish on the small parts smacks of immediate post-war shortages of fripperies like chrome for plating. Despite (because of?) this, it is a solid, well constructed, item and the small parts are accurately machined.
Strangely the branding is upside down - unlike the later Favorit version.