Vintage 1973 JAPAN GRAND SEIKO CALENDAR 5645-7010 25Jewels Automatic.

Vintage 1973 JAPAN GRAND SEIKO CALENDAR 5645-7010 25Jewels Automatic.

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

Item description

Movement :

• Pet name : 56 GRAND SEIKO CALENDAR .
• Caliber number : 5645A.
• Movement : Automatic.
• Beat rate : 28800bph.
• Year of manufacture start : 1970's.
• Factory : Suwa.

Externals :

• Serial number : 370817.
• Dial number : JAPAN 5645-7020T.
• Glass : Crystal.
• Case size : About 36.8mm.
• Lug width : 18mm.
• Band : New Leather Strap of SEIKO original.

Condition :

• Used, it runs well.
• Quick set(Day/Date) : Okay.
  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.

Key Features

The Sovereign Benchmark of 1973 Suwa Grand Seiko Luxury (1973): Manufactured in **1973**—a historic milestone year representing the apex of late-Showa mechanical watchmaking refinement—the **Grand Seiko Calendar (56GS)** stood as Suwa Seikosha's ultimate statement in executive automatic performance. Sourced under reference **5645-7010**, this date-only flagship instrument was factory-adjusted to strict internal chronometer standards, serving as an authoritative status symbol for high-society executives during the peak of Japan's post-war economic miracle.

The High-Beat 25-Jewel Caliber 5645 Automatic Heart: Powering this historic timepiece is the legendary **25-jewel Caliber 5645A**, an in-house automatic engine operating at a swift high-beat frequency of **28,800 vibrations per hour (8 beats per second)**. Highly celebrated by vintage purists for its remarkably ultra-thin architecture and uncompromised chronometric stability, this movement deploys a lavish **25-jewel specification** to control gear-train friction. It incorporates modern executive conveniences including **hacking seconds**, quick-set date calendar functionality, and smooth manual-winding capability.

Architectural ""7010"" Grammar of Design Case Geometry: The reference **5645-7010** is globally distinguished among serious collectors for its textbook execution of Taro Tanaka's foundational **""Grammar of Design""** guidelines. The solid stainless steel case features extraordinarily sharp, broad-shouldered facets and muscular, mirror-polished bevels engineered to reflect light without distortion. This low center-of-gravity design allows the mechanical instrument to sit completely flush against the wrist, sliding weightlessly under a tailored shirt cuff.

Immaculate Date-Only Dial Harmony and Clinical Clarity: The dial of the **5645-7010** is a masterclass in mid-century visual restraint and high-contrast clarity. Free from day-window clutter, it features **hand-applied, multifaceted hour indices** paired with razor-sharp dauphine hands that capture light with striking contrast. Symmetrically framed at 3 o'clock, the quick-set date window delivers instant split-second legibility, proudly signed with the applied **""GS"" logo** and the Suwa electronic symbol above 6 o'clock.

The Iconic Solid Gold GS Medallion or Engraved Back Heritage: The ultimate hallmark of this 1973 treasure sits proudly on the case back: the legendary **solid gold-embossed Grand Seiko medallion** (or deeply engraved GS logo). This crest historically certified its elite manufacturing status and supreme, factory-regulated timing precision. Built to an uncompromising heirloom standard that effortlessly transcends passing fashion trends, the 5645-7010 stands as an eternal, investment-grade testament to the golden era of Japanese automatic engineering.

For more information, please look at the pictures.

Notes

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