Vintage 1971 JAPAN GRAND SEIKO CALENDAR 5645-7010 25Jewels Automatic.

Vintage 1971 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 : 161666.
• Dial number : JAPAN 5645-7010T.
• Glass : Crystal.
• Case size : About 36.5mm.
• 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 Peak of 1971 High-Grade Chronometry (1971): Manufactured in **1971**—a historic milestone year during the apex of Suwa Seikosha's mechanical achievements—the **Grand Calendar** represented the gold standard of Japanese high-precision watchmaking. Sourced under reference **5645-7010**, this high-grade automatic timepiece was engineered to deliver uncompromising internal chronometric accuracy paired with Taro Tanaka's iconic grammar-driven design language.

The Over-Engineered High-Beat 25-Jewel Caliber 5645 Heart: Powering this legendary instrument is the in-house **25-jewel Caliber 5645A**, operating at a swift high-beat frequency of **28,800 vibrations per hour (8 beats per second)**. Regulated at the factory to strict internal Grand standard specifications, this movement features **hacking seconds**, smooth manual-winding capability, a quick-set date mechanism, and micro-adjuster rate regulation.

Architectural ""7010"" Grammar of Design Case Geometry: The reference **5645-7010** is globally revered among vintage collectors as one of the purest expressions of the **""Grammar of Design""** philosophy. Executed in solid stainless steel, the case features flat, mirror-polished Zaratsu facets, razor-sharp lug lines, and geometric angles engineered to reflect light cleanly without visual distortion.

Immaculate Date-Only Dial Balance and Clinical Precision: The dial of the **5645-7010** exhibits exceptional visual restraint, showcasing a radiant silver canvas decorated with **hand-applied, multifaceted rectangular hour indices** with dark center inserts. Symmetrically framed at 3 o'clock, the date calendar window provides sharp legibility, perfectly offset by the applied **""GS""** emblem and bold **""HI-BEAT""** typography above 6 o'clock.

The Sovereign Solid Gold GS Case Back Medallion: The ultimate seal of authenticity and prestige sits proudly on the case back: the iconic **solid gold GS medallion** set flush into the stainless steel backplate. Certified to elite internal accuracy standards, the 5645-7010 Grand stands as an eternal, investment-grade cornerstone reference for serious vintage horological collectors worldwide.

For more information, please look at the pictures.

Notes

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