Hi everyone, Up for sale is one of Longines’ finest innovations from the late 1960s: the Ultra-Chron ref. 8353, powered by the high-beat Cal. 431 chronometer movement running at 36,000 bph. These were Longines’ answer to the high-beat race of the era, delivering precision and smooth sweep far ahead of many contemporaries. This example features the distinctive cushion-style stainless steel case and a date window positioned uniquely at 4 o’clock. The vertically brushed two-tone dial catches light beautifully, shifting in tone depending on the angle. Freshly serviced in August 2025, it’s running strong at \~+10s/day, amplitude \~240, and beat error \~0.2. **Condition** * **Dial:** Original two-tone dial with vertical brushing. Shows a visible scratch near 12 o’clock (see macro), but the dial still presents well and plays with light beautifully on the wrist. * **Case:** 35mm stainless steel cushion case, unpolished, with natural wear and hairline scratches. * **Crystal:** Unsigned plexi. * **Crown:** Original signed Longines crown, period correct for the reference. * **Movement:** Longines Cal. 431 high-beat chronometer. Fully serviced Aug 2025, running well at 36,000 bph. * **Strap:** Aftermarket leather strap with unsigned buckle.