COMMODORE SPORT TIME MASTER LED 1976
This is an extremely rare all plastic Commodore Time Master from approximately 1975/76 by Commodore Business Machines (CBM). It's a first batch watch with early American-made module in Palo Alto, California what has been clearly marked on the caseback. The US module with flat red filter on top is the best Commodore LED technology that is hard to come by. The case is not really typical plastic as the material used is called Polysulfone, a high-tech and expensive (transparent!) industrial techno-polymer known for its properties to withstand deformation when exposed to hazardous acids and heat up to 180°C. As a cost-effective alternative to glass it must have been a space-age material back in those days :)
CBM moved to Europe and Hong Kong shortly after where cheap modules with significantly (4x) smaller diodes were produced until approximately 1978. The late generation modules have ugly magnifying lenses that dramatically interfere with the shape of displayed digits so whenever possible upgrade your Commodore to the rare early American modules. Cheaper plastic sports versions were also made but the quality and design is not even close to the early type. As the case is non-conductive the inside is covered with metal that must connect properly with the caseback to activate a function upon pressing a button. Broken button contacts can be repaired with a piece of metal from a beer can as pictured below. The early Polysulfone case has these contacts made in a far more advanced way with two separate and slightly raised contacts that connect a metal plate on the caseback.
Keywords: commodore led, time master
Market value: 50-150$ (condition, box)