Casio Pro Trek PRT-311 “Twin Sensor” – Japan Made – Titanium Back & Bracelet – 1990s Here we present a vintage Casio Pro Trek from the early generation of outdoor digital watches, equipped with the iconic “Twin Sensor” system. The PRT-311 is a derivative of the PRT-30 series and represents one of the early Pro Trek models developed during the 1990s, when Casio was actively expanding its outdoor and adventure watch lineup. This model features a robust construction with a titanium caseback and titanium bracelet, offering both durability and a relatively lightweight feel compared to standard stainless steel models. The distinctive industrial design, including the metal side buttons (“mushroom-style” pushers), gives the watch a rugged and tool-like appearance characteristic of early Pro Trek models. Both the caseback and inner clasp are marked “JAPAN”, confirming this is a Japan-made piece from the period. Functions Timekeeping: OK Mode switching: Working Alarm: Working Stopwatch: Working Backlight: Working Twin Sensor display: reacts and shows bar graph indication when activated (However, accuracy and full functionality of sensor measurements are not verified) Battery replaced a few months ago. Condition This is a vintage digital watch in working condition. Visible scratches on the crystal (material unknown) Noticeable wear, scratches, and marks on bezel, case, and bracelet Typical signs of use consistent with age, especially on titanium surfaces Overall condition should be judged from the photos Size Case diameter: approx. 45 mm Wrist size: approx. up to 18 cm (adjustable by removing links) Notes No box or papers. Watch only. As a vintage digital watch, long-term performance, sensor accuracy, and water resistance cannot be guaranteed. A rare opportunity to acquire an early Japan-made Pro Trek with titanium construction and classic Twin Sensor functionality — a piece that reflects Casio’s pioneering era in outdoor watch development.