Seiko - Seiko 5 Sports Speed-Timer Chronograph - No reserve price - 6138-0011 - Men - 1970-1979

Up for sale is an iconic and historically significant vintage men's Seiko 5 Sports Speed-Timer chronograph, known to enthusiasts and collectors worldwide by the nicknames "UFO" or "Yachtman" (Reference 6138-0011).
Produced in June 1976 (as confirmed by serial number 669006 engraved on the case back), this example belongs to the prized and highly sought-after JDM (Japan Domestic Market) variant. Unlike models destined for global export, the JDM version stands out for the prestigious inscription SEIKO Speed-Timer on the original black dial, as well as the JAPAN J marking on the case back and the bilingual day wheel (English/Kanji).
The 44 mm stainless steel case (excluding crown) with a 15 mm thickness features the distinctive oval, lugless architecture reminiscent of a flying disc, from which the famous nickname "UFO" stems. On the top, the famous black and red bi-colored fixed tachymeter bezel with a tachymetric scale stands out, designed for calculating average speed.
The beating heart of the watch is the legendary Seiko Caliber 6138B, an automatic chronograph movement with manual winding via the crown. This caliber represents a milestone in 1970s Japanese watchmaking thanks to its refined integrated architecture with column-wheel control and vertical clutch, ensuring maximum precision and responsiveness of the chronograph display. The dial features the two-register asymmetric configuration "Big Eye / Small Eye" (hour register at 12 and 30-minute register at 6) and the dual date complication with quick-set at 3 o’clock.
Condition of the item:
Esthetically the watch is presented in its original, unrestored state, showing evident and fascinating signs of wear due to age and daily use (surface scratches and patina on the stainless steel case, the tachymeter bezel, the Hardlex mineral crystal, and the contemporaneous stainless steel bracelet). This authentic patina gives the timepiece a distinctive vintage character. Mechanically, the movement runs perfectly: timekeeping is good, the chronograph functions start, stop, and reset correctly, and the quick day/date change is fully operational.
A fundamental piece of automatic chronograph history, indispensable and of great collecting value.