The Watchismo blog has a nice history of the first calculator watch prototypes:
Litronix, primarily an LED supplier to the other vintage digital watch brands including the first Hamilton-Pulsar digital watches. Featured here are these two experimental prototype calculator concept watches Litronix was considering for development.But what makes this strange watch special is the unusual feature of sliders instead of buttons. Likely an attempt to improve the data entry from multiple miniature buttons to a more tactile sliding mechanism. The sliders move over a commutator which is a pc board segment. I assume you move them to the desired number and press down for selection but it sure seems like a waste of time. I guess that's why it never went into production, huh? Maybe someone can let me know if this slider function has ever been developed into another product from that time.
See also:
History of slide-rule wristwatches
Early days of plastic watches
Mechanical "LED watch" from 1970
History of calculator watches
Steampunk watch
Belt-drive watch
Watch guts of great beauty
All-plastic watch movement from the 70s
Awesome, impractical, expensive watch
