Vintage 1965 JAPAN SEIKO SEIKOMATIC-R SLIMDATE 8305-1010 30Jewels Automatic.

Vintage 1965 JAPAN SEIKO SEIKOMATIC-R SLIMDATE 8305-1010 30Jewels Automatic.

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

Item description

Movement :

• Pet name : 83 SEIKOMATIC-R CALENDAR .
• Caliber number : 8305B.
• Movement : Automatic.
• Beat rate : 18000bph.
• Year of manufacture start : 1963's.
• Factory : Suwa.

Externals :

• Serial number : 5N31444.
• Dial number : JAPAN 8305-1020TAD.
• Glass : Acrylic.
• Case size : About 38.08mm.
• Lug width : 20mm.
• 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 Milestone of Mid-60s ""Slim"" Corporate Luxury (1965): In **1965**, the **Seiko Seikomatic-R Slimdate** stood as a highly sophisticated lifestyle statement for Japan's emerging class of young executives and white-collar professionals. The reference **8305-1010** was produced by the **Suwa Seikosha** factory during a landmark historical period when Japanese industry was pivoting toward sleeker, ultra-low-profile architecture. Designed specifically to target the ""Business-A"" market, it countered the heavy, chunky automatic watches of the early 60s by delivering an incredibly thin, sharp daily instrument that radiated metropolitan confidence and technical pride.

The Advanced 30-Jewel Caliber 8305 Ultra-Thin Heart: This watch is powered by the magnificent **30-jewel Caliber 8305** (specifically Cal. 8305C), a high-grade automatic movement operating at **18,000 vibrations per hour (vph)**. In **1965**, a **30-jewel count** was a definitive hallmark of luxury engineering, utilizing extra synthetic rubies to secure the calendar and automatic gear trains. Breaking away from Seiko's traditional Magic Lever system, Suwa engineers developed a specialized **roller-bearing gear-driven winding assembly**, which successfully shaved over 1 mm off the movement's thickness to pioneer a whole new era of mechanical slimness.

Architectural ""1010"" Oversized Contemporary Case Geometry: The reference **8305-1010** is highly celebrated among vintage purists for its distinctively modern, forward-thinking proportions. To compensate for the widened profile of the flattened 83-series movement, Seiko expanded the stainless steel case to a commanding **38mm diameter with 20mm lugs**—an exceptionally bold and contemporary dimension for **1965**. Featuring sharp, elegant lugs and a polished low-profile bezel, the case sits perfectly flat and flush on the wrist, sliding effortlessly under a tailored bespoke suit cuff.

Masterful ""Slimdate"" Visual Symmetry and Reflection: The dial of the **8205-1010** is a study in clinical mid-century luxury, showcasing a radiant, rhodium-plated silver sunburst finish. By omitting the day window and focusing entirely on a clean **""Slimdate"" configuration at 3 o'clock**, the watch achieves breathtaking visual balance. This canvas is paired with **hand-applied, multifaceted elongated baton indices** and sharp hands that create an elegant play of light. The cursive, printed **""Seikomatic-R"" logo** above 6 o'clock remains a prestigious badge of industrial craftsmanship.

A Landmark of Suwa's High-Jewel Automatic Legacy: Produced in the milestone year of **1965**, the 8305-1010 remains a highly coveted ""connoisseur's grail"" for vintage collectors who value the evolutionary history of the Seikomatic family. It represents the perfect historical intersection where rugged daily utility met the peak of 1960s minimalist architectural restraint and high-jewel micro-engineering. Originally featuring the iconic **Dolphin or Whirlpool etching** on the case back, it stands as a profound testament to an era when Japan perfected the high-utility executive dress watch for the global stage.

For more information, please look at the pictures.

Notes

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