This is a vintage CITIZEN COSMOTRON reference 4-790821 wristwatch from the 1970s, featuring a classic electronic COSMOTRON movement with recent battery change (February 2026) and currently running. It has a rare green dial with day-date display in Japanese. The stainless steel case and bracelet show moderate signs of use, including surface scratches and wear consistent with age. The crystal has light surface marks. The dial exhibits natural aging that contributes to its vintage character. This watch is ideal for collectors and enthusiasts of vintage Japanese electronic timepieces.