In addition to the two yellow illuminated advertising installations, there is another installation with blue illuminated tubes in the form of single letters on the facade above the second floor.
This installation is currently out of operation. It was commissioned or installed in August 1965 by Mr. Walter Mächtlinger on the occasion of the relocation of the bookstore to the then newly constructed building at Pfinztalstrasse 36. The manufacturer was the company NEON-Martin, Karlsruhe.
Many thanks to Mrs. Monika Lorek for the information!
In the photo from 2005, the building can be seen on the left; the device is switched on.