Vintage 1971 JAPAN GRAND SEIKO WEEKDATER 5646-8000 25Jewels Automatic.

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

Item description

It's a Automatic Watch, GRAND SEIKO WEEKDATER 5646-8000 25Jewels .
It's in good used condition.
It's difficult to find this valuable watch in such a good condition. Highly recommended for collectors!
Movement :
  • Pet name : 56 GRAND SEIKO WEEKDATER .
  • Caliber number : 5646A.
  • Movement : Automatic.
  • Beat rate : 28800bph.
  • Year of manufacture start : 1970's.
  • Factory : Suwa.
Externals :
  • Serial number : 1N0767.
  • Dial number : JAPAN 5645-8000T.
  • Glass : Crystal.
  • Case size : About 35.7mm.
  • Lug width : 18mm.
  • Band : New Leather Strap of SEIKO original.
Condition :
  • Used, it runs well.
  • 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.
  • The day difference time of an used watch is about +-1 minute / day.
  • For practical, everyday use, it would be advisable to have the movement cleaned and oiled.
  • There are chips visible all along the edge of the glass.
Key Features
  • The Pinnacle of Suwa Mechanical Mastery (1971): In **1971**, the **56 Grand (56GS)** represented the absolute peak of automatic precision before the industry shifted toward quartz. The reference **5646-8000** was produced by the **Suwa Seikosha** factory during a landmark era of horological achievement. It arrived as a high-frequency instrument of clinical accuracy, intended to provide the global elite with a ""Grand"" standard of timekeeping that surpassed the finest Swiss chronometers.
  • The High-Beat Caliber 5646 Heart: This watch is powered by the **25-jewel Caliber 5646A**, a sophisticated automatic movement operating at **28,800 vibrations per hour (8 beats per second)**. In **1971**, this ""Hi-Beat"" frequency was engineered to provide superior stability against external shocks. The 56-series was a breakthrough in slim-profile design, featuring **hacking seconds**, manual winding capability, and an instantaneous day-date change, all housed within a remarkably thin architecture.
  • Purest Execution of the ""Grammar of Design"": The reference **5646-8000** is a definitive example of the **Style**. The case features flat, mirror-polished surfaces and razor-sharp, multifaceted lugs designed to catch and reflect light with surgical precision. In **1971**, this architectural rigor followed the principles of Taro Tanaka, ensuring the watch would ""sparkle"" on the wrist and visually communicate the high status and professional discipline of its owner.
  • Masterful ""Weekdater"" Dial Symmetry: The dial of the **5646-8000** is a study in functional luxury, featuring a radiant sunburst silver finish and **hand-applied, multi-faceted baton indices**. The dual-calendar window at 3 o'clock houses a **bilingual (English/Kanji) day disk**, providing an organized, professional aesthetic. The applied **""GS"" logo** and the Suwa factory symbol at 6 o'clock remain iconic hallmarks of this era’s uncompromising quality and prestige.
  • A Landmark of Showa-Era Horological Art: Produced in **1971**, the Grand 5646-8000 remains one of the most coveted ""Grail"" watches for vintage collectors worldwide. It represents the final, glorious peak of the mechanical era, combining **heavy-duty engineering with a timeless, minimalist aesthetic**. It stands as a testament to the era when Suwa Seikosha perfected the high-end automatic, creating a mechanical masterpiece that remains as accurate and visually stunning today as it was half a century ago.
    • For more information, please look at the pictures.
    Notes
    • Before buying.
      The vintage watches we sell are inspected and adjusted so they work fine. However, since it is an vintage watch, Please purchase on the assumption that it will be repaired.

    • To prevent shipping accidents.
      Please monitor the tracking number until the item arrives and if it stagnates, please investigate at your country post office. Also, please confirm the item when you receive the item.

    • About import taxes.
      Taxes such as import duties and VAT are not included in the item price or shipping charges, except for items shipped to the US. When you purchase, you will likely be required to pay these fees in your country.

    • About Payment, Shipping, Return.
      Payment, Shipping, Return are in accordance with eBay's business policies.