Updating…
Very unusual and historically important, probably unique prototype of Lemania LED 0.925 sterling silver wristwatch, made in 1970s. Diameter is 30 mm. Caseback is engraved 645 LED. The LED module/movement is produced by Collins (one of American LED suppliers).
United States was leading the global quartz watch revolution. For example from 1972 to 1974, Omega had purchased about 30,000 LED modules from Pulsar to use in Omega Time Computer watches. Lemania produced movements for Omega and probably tried to jump onto the last carriage of the departing LED train.
Watch is in overall good condition, running and ready to wear!