Serviced Vintage 1971 JAPAN SEIKO 5 SPORTS SPEED-TIMER 6138-0020 21J Automatic.

Serviced Vintage 1971 JAPAN SEIKO 5 SPORTS SPEED-TIMER 6138-0020 21Jewels Automatic.

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

Item description

Movement :

• Pet name : 61 5 SPORTS SPEED-TIMER.
• Caliber number : 6138A,B.
• Movement : Automatic.
• Beat rate : 21800bph.
• Year of manufacture start : 1970's.
• Factory : Suwa.

Externals :

• Serial number : 142740.
• Dial number : JAPAN 6138-0030T.
• Glass : Crystal.
• Case size : About 42.16mm.
• Lug width : 20mm.
• Band : New Leather Strap.

Condition :

• Used, it runs well.
• Function is good.
  Day of the week can be set in English or Kanji.
  Quick set(Day/Date) : Okay.
  Set of the days of the week : The set at one stage pulling the crown.
  Set the date: The set at one stage pulling the crown.
• The day difference time of an used watch is about +-1 minute / day.
• Overhaul service in February 2026.
  The movement has been cleaned and oiled, so it works fine.

Key Features

The Pinnacle of Automatic Chronographs (1971): By **1971**, Seiko was at the forefront of the global race for automatic chronographs. The reference **6138-0020** was a flagship of the **5 Sports Speed-Timer** line, designed for the ""active generation."" It showcased Seiko’s dominance in precision timing, being one of the first reliable, mass-produced automatic chronographs with both a 12-hour and 30-minute recorder.

The Legendary Caliber 6138: This watch is powered by the **21-jewel Caliber 6138**, a robust high-beat heart operating at **21,600 vibrations per hour (vph)**. Horologically, it is famous for featuring a **column wheel and a vertical clutch system**—features typically found only in the most expensive Swiss chronometers today. Unlike its predecessor (the 6139), the 6138 added **manual winding capability**, making it a favorite for its mechanical versatility.

Iconic ""Tokei Zara"" Helmet Case: The reference **6138-0020** is legendary for its unique, futuristic case shape, often nicknamed the **""Helmet""** or **""Tokei Zara"" (Clock Dish)** in Japan. In **1971**, this bold, streamlined design—with its hidden lugs and towering profile—represented the height of Space Age industrial aesthetics, ensuring the watch stood out as a specialized instrument on the wrist.

Racing-Inspired Dial and Tachymeter: Designed for the racetrack, this model features a high-contrast dial with an internal tachymeter scale. The dual-subdial layout at 12 and 6 o'clock provides a perfectly balanced vertical symmetry. In **1971**, the use of vibrant orange or yellow chronograph hands was a deliberate choice to ensure **split-second legibility** during high-speed activities.

The ""5 Sports"" Pedigree: As part of the **Seiko 5 Sports** family, the 6138-0020 met five essential criteria: automatic winding, day-date calendar, water resistance, a recessed crown, and a durable case. Produced by the **Suwa Seikosha** factory, it remains one of the most culturally significant and collectible chronographs in Seiko’s history, embodying the spirit of 1970s innovation.

For more information, please look at the pictures.

Notes

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