East German endless-loop compact cassette for answering machines. Made by VEB Kunstseidenwerk "Friedrich Engels" in Premnitz (see inner side photos <a rel="nofollow" class="external autonumber" href="https://rft-geraete.de/Zubehoer/Sonderversionen">[1]</a>. Supplied with RFT-made answering machines.
<a href="//commons.wikimedia.org/wiki/User:Stefan_K%C3%BChn" title="User:Stefan Kühn">Stefan Kühn</a>
<span class="int-own-work" lang="en">Own work</span>