For the discerning collector, this watch is more than a timepiece—it is a piece of horological history. • The Last In-House Giant: The Calibre L990 (featured here) was Longines' final in-house automatic movement. Released in 1977 during the height of the Quartz Crisis, it was a "mechanical masterpiece" intended to prove that Swiss watchmaking was still supreme. • A World Record Holder: Upon its release, it was the thinnest automatic movement in the world to feature both a central seconds hand and a date function. • Twin-Barrel Engineering: Unlike standard movements of the era, the L990 utilizes twin barrels (two mainsprings). This high-end architecture provides a more constant flow of energy, ensuring superior accuracy (isochronism) even as the watch winds down. • The Lemania Legacy: The design of this movement was so exceptional that when Longines joined the Swatch Group, the rights were sold to Lemania, who used it to power high-end watches from brands like Breguet. A beautiful example of horological history: the Longines Reference 4392, housing the iconic Calibre L990. This movement represents a milestone in watchmaking; it was Longines' final in-house automatic caliber and held the title of the world’s thinnest automatic movement with twin barrels for many years. To this day, the design of this movement is so respected that the plans were eventually sold to Lemania (becoming the Lemania 8810). Condition Report: • Movement: The heart of this watch is the high-grade, 25-jewel Calibre L990.1. It is running accurately and the automatic winding mechanism functions smoothly. • Dial: Classic white dial with elegant Roman numerals and a date window at 3 o'clock. The dial remains in original condition with a light, honest patina that adds vintage character. • Case: Gold-plated "Tonneau" style case. It shows some signs of wear consistent with age (please see photos), but retains its sharp lines. • Crystal: Fitted with a brand new aftermarket crystal, ensuring a clear and scratch-free view of the dial. • Bracelet: Comes on its original integrated-style gold-plated bracelet. Note: The bracelet has been previously repaired with solder on the underside (visible in photos). While it is secure and perfectly wearable, this is mentioned for full transparency.