Vintage 1978 JAPAN SEIKO GROUND TWIN-QUARTZ 9943-800A 5Jewels Quartz.

Vintage 1978 JAPAN SEIKO GROUND TWIN-QUARTZ 9943-800A 5Jewels Quartz.

Welcome to my auction!
I am Japanese who live in Tokyo.

Item description

Movement :

• Pet name : 99GQW GROUND QUARTZ.
• Caliber number : 9943.
• Movement : Quartz.
• Year of manufacture start : 1978's.
• Factory : Suwa.

Externals :

• Serial number : 830451.
• Dial number : JAPAN 9943-8000 T.
• Glass : Crystal.
• Case size : About 35.5mm.
• Lug width : 19mm.
• Band : New Leather Strap of SEIKO original.

Condition :

• Used, it runs well. Battery replaced
• Quick set(Day/Date) : Okay.
  Set the day of the week can be in English or Kanji.
  Set of the date : The set at one stage pulling the crown.
  
• Approximate watch rate at Japan : Quartz.
• For practical, everyday use, it would be advisable to have the movement cleaned and oiled.

Key Features

The Sovereign Apex of 1978 High-Precision Luxury (1978): Manufactured in **1978**—a historic milestone year representing the ultimate pinnacle of Japan's electronic horological revolution—the **Seiko Grand Twin-Quartz** stood at the absolute top tier of Suwa Seikosha's executive collection. Sourced under reference **9943-800A**, this flagship timepiece inherited the supreme prestige of the Grand Seiko line, offering unmatched ultra-high precision wrapped in sharp, forward-looking late-1970s Showa-era styling.

The Revolutionary 5-Jewel Caliber 9943 Twin-Quartz Engine: Powering this historic watch is the legendary **5-jewel Caliber 9943**, an in-house electronic masterpiece utilizing dual paired quartz crystal oscillators. One crystal provided standard timekeeping frequency, while the second detected ambient temperature fluctuations to continuously self-adjust and offset thermometric drift. Built with a robust **5-jewel specification** to control gear-train pivot wear, it achieved an astonishing accuracy standard of within **±10 seconds per year**, featuring **hacking seconds** and quick-set dual calendar functionality.

Architectural ""8000"" Angular Case and Integrated Geometry: The reference **9943-800A** is globally distinguished among vintage collectors for its distinct, sharp-edged integrated case architecture. Executed in solid stainless steel, the case features flat, razor-sharp facets and sweeping, angular lug contours finished with zero-distortion mirror polishing inspired by Taro Tanaka's **""Grammar of Design""** principles, allowing the watch to sit remarkably flat and balanced on the wrist.

Masterful Textured Dial and Applied Twin-Quartz Emblem: The dial of the **9943-800A** showcases remarkable depth, featuring a fine textured canvas paired with **hand-applied, multifaceted rectangular hour indices** and razor-sharp hands. Symmetrically framed at 3 o'clock, the dual-calendar window houses a **bilingual (English/Kanji) day disk** alongside the date wheel, proudly bearing the applied **""GRAND QUARTZ""** typography and the iconic double-comb **Twin-Quartz logo** above 6 o'clock.

An Investment-Grade Masterpiece of Suwa's Electronic Heritage: Manufactured in the milestone year of **1978**, the 9943-800A Grand Twin-Quartz remains one of the most historically significant, highly sought-after cornerstone references for serious vintage Seiko collectors worldwide. It captures the exact historical moment where Japanese electronic engineering achieved supreme luxury status alongside mechanical horology. Built to an uncompromising heirloom standard, it stands as an eternal testament to late-1970s Japanese watchmaking innovation.

For more information, please look at the pictures.

Notes

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