Seiko 5 Automatic Moonphase | Genta Design

Seiko Seiko 5 Automatic Moonphase Ref. 6347-5000 | Octagonal Case | Black Inner Bezel | 1980s Description This Seiko 5 Automatic Moonphase Ref. 6347-5000 is one of the most distinctive mechanical watches Seiko ever produced. Architectural, technically ambitious, and unmistakably of its era, it stands apart from the brand’s more familiar sports models. The stainless steel octagonal case, measuring approximately 35 × 38 mm, delivers strong Gerald Genta–era design language. Sharp facets, balanced proportions, and an integrated visual flow give the watch a confident presence without excess bulk. While not a direct Genta design, the influence is unmistakable and intentional. The midnight blue dial is framed by a black inner bezel, not gold, giving this example a more restrained and contrast-driven look. Applied markers, a clean minute track, and the subtle framing of the dial keep the layout legible and composed. The moonphase display is integrated discreetly below the dial surface, adding complexity without visual clutter. Powering the watch is the Seiko Calibre 6347, the only automatic moonphase movement Seiko ever produced. This alone places the reference in a unique position within Seiko’s history. The movement combines reliability with a complication typically reserved for far more expensive Swiss watches of the period. The watch is fitted with a non-original stainless steel bracelet, suitable for daily wear but clearly disclosed as aftermarket. Specifications • Brand: Seiko • Model: Seiko 5 Moonphase • Reference: 6347-5000 • Year: Circa 1980s • Movement: Automatic, Seiko Calibre 6347 (moonphase) • Case Material: Stainless steel • Case Shape: Octagonal • Case Dimensions: Approx. 35 × 38 mm • Dial: Midnight blue • Inner Bezel: Black • Bezel: Stainless steel • Moonphase: Integrated, recessed display • Crystal: Mineral • Bracelet: Stainless steel, aftermarket • Lug Width: 18 mm • Functions: Hours, minutes, seconds, date, moonphase • Water Resistance: Originally splash resistant, not guaranteed due to age Condition Report • Dial: Original dial in very good vintage condition with clean printing and even aging. • Case: Stainless steel case showing light wear consistent with age; edges remain well defined. • Bezel: Stainless steel bezel in good condition with normal signs of use. • Crystal: Mineral crystal with light surface marks visible under strong light. • Movement: Seiko Cal. 6347 automatic moonphase movement running smoothly. • Bracelet: Aftermarket stainless steel bracelet in good wearable condition. Historical Significance The Seiko 5 Moonphase Ref. 6347-5000 represents a short and ambitious chapter in Seiko’s mechanical history. Introduced in the 1980s, it showcased Seiko’s willingness to explore complex complications within an accessible automatic platform. The Calibre 6347 remains the only automatic moonphase movement ever produced by Seiko, making this reference especially desirable among collectors of Japanese horology. The bold octagonal case and restrained dial execution place this watch firmly within the post-Genta design era, offering architectural flair without imitation. It’s a watch that rewards collectors who value originality, technical rarity, and design integrity.