Berliner TT Bahnen, in short BTTB, was created in 1972 when the DDR government took over the control of Zeuke & Wegwerth. With this take over, Zeuke left the company. BTTB changed the focus from innovation and quality to much more a quantity production. Export to gain hard currencies was the main goal. In its top production time, there were around 800 employees making 5000 models a day.
In 1989 the unification between the DDR and West Germany was a fact. In those days the state guided companies were again independent and self controling. Zeuke was shortly asked in 1990 to lead the company. With new products and a new cataloque he tried to get more attention. But after one year a new manager was introduced: Carlo Parisel. Also this manager with a marketing background tried to get more attention to models. The boxes were changed and became much more professional. But he could not save BTTB from bankruptcy.
What's it worth? Take a look at this Bttb price guide: sold listings for a value indication.