1975 – Nepro Solar
Nepro was a Swiss company known for innovative watches. The internal electronics were purchased from Ness Time, the manufacture of the Synchronar at that time. The case design allows for the battery to be changed. I have also seen versions of this watch sold under the names and brands: Meister Anker, LOV, and Alfatronic.
Comment: The case is a wonderful design, truly unique - unlike any design before or since.