Here are a few of the ELCASET prototypes presented in Japanese magazines and hifi shows between 1976 and 1979.
SONY ELCASET preproduction/ prototype from 1976.
With minor changes this became the SONY EL-7 model in 1977.
With minor changes this became the SONY EL-7 model in 1977.
Technics ELCASET prototype as seen in a 1976 Japanese magazine.
TEAC ELCASET prototype as seen in a 1976 Japanese magazine.
SONY ELCASET EL-D9 presented at a Hi-Fi show. If I understand correctly the model now belongs to a collector.
Technics RS-7900U ELCASET prototype from a private collection in Germany.
SONY ELCASET as envisioned by a SONY fan. This is not a real model, not even a prototype just a fun project by member Vincei from the Audiokarma forum.
You can see all the manufactured ELCASET models in this previous post.