The story of FuS brand may go something like this... . In order to escape bombing at its other locations Fichtel & Sachs (F&S) set up a plant in 1942/3 in Reichenbach (near Chemnitz the home of Diamant, East Germany’s leading bicycle producer).
After 1945 this plant became a separate business (VEB) when Reichenbach became part of the DDR. VEB stands for ‘Volkseigener Betrieb’ (‘organisation owned by the people’), and was the standard form of state owned business in the DDR.
From about 1949 this business used the FuS brand, implicitly standing for ‘Fichtel und Sachs’ but being ever so slightly different from ‘F&S’. In 1954 it decided to stand on its own two feet and replaced the FuS brand with the Renak brand. Renak was a contraction of Reichenbacher Naben- & Kupplungwerke (Reichenbach Hub & Clutch Factory) .
I know relatively little about FuS products, but the Renak brand covered a wide range of cycle components, and one can only assume that the FuS brand did the same.