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The Encyclopedia of Horology

Wristwatch · Chronograph

Seiko Calculator Chronograph 6138-7000

Partially verified

This Seiko Calculator Chronograph, reference 6138-7000, dates to 1971. The watch features a 45 mm stainless steel case and is notable for its integrated slide rule bezel, which includes a secondary transparent plastic indicator for mathematical calculations. The dial is matte black with metallic grey sub-registers, accented by orange chronograph hands and ivory-toned luminous markers. Powering the watch is the automatic Seiko caliber 6138, the brand's first dual-register chronograph movement. It is fitted with an original Seiko steel bracelet. The watch has been recently serviced according to the source. It is presented without original documentation or packaging. The case has undergone a light polish while retaining its original dimensions. The slide rule bezel remains in black with minor signs of wear. The crown, push-pieces, and case back are present.

Front view of the Seiko Calculator Chronograph 6138-7000, displaying the matte black dial and the slide rule bezel with transparent indicator.
Front view of the Seiko Calculator Chronograph 6138-7000, displaying the matte black dial and the slide rule bezel with transparent indicator. — Zamanito. Rights pending — permission not yet requested. Original source

Catalogue identity

Source
zamanito.com
Category
Wristwatch · Chronograph
Maker / attribution
Seiko
Reference
6138-7000
Catalogue / lot identifier
Source URL identifies the listing
Source-reported date
1971
Source-reported place
Japan

Source-reported attribution and specifications are not independent authentication. A listing does not establish present ownership, current display, availability or permission to reproduce.

Object description

Design and Dial

The watch features a 45 mm stainless steel case, which the source reports has undergone a light polish but maintains its original angles and proportions. The matte black dial is configured with two metallic grey sub-registers and ivory-colored luminous markers. Orange hands are utilized for the chronograph functions, providing visual coordination with the orange markings on the slide rule bezel.

A distinctive feature of this model is the functional slide rule bezel in black, equipped with a secondary transparent plastic indicator. This mechanism is designed to facilitate mathematical calculations. The watch includes a day and date display aperture on the dial.

Evidence for this section
  • “قاب فولادی ضدزنگ این ساعت با قطر ۴۵ میلی‌متر طراحی شده و طبق توضیحات منبع در گذشته یک پولیش ملایم دریافت کرده”
  • “زه مشکی ماشین‌حساب ثبات رنگ خود را حفظ کرده و تنها آثار خفیف استفاده را نشان می‌دهد”
  • “عقربه‌های فرعی و عقربه مرکزی کرنوگراف به رنگ نارنجی هستند”

Movement and Technical Specifications

Internally, the watch is driven by the Seiko caliber 6138 automatic movement. This caliber, which succeeded the 6139, is identified as the brand's first dual-register chronograph movement. The configuration allows for a comprehensive chronograph display in an automatic format.

The watch includes a day and date complication integrated into the dial. The source states that the movement has been recently serviced and provides accurate timekeeping performance.

Evidence for this section
  • “مجهز به کالیبر اتوماتیک 6138 سیکو است که پس از کالیبر شناخته‌شده 6139 معرفی گردید و نخستین کالیبر دو ثبته (dual-register) این برند محسوب می‌شود”
  • “این ساعت اخیراً سرویس شده و کارکرد زمانی دقیقی را ارائه می‌دهد”

Bracelet and Condition

The watch is provided on an original Seiko steel bracelet. According to the source, the bracelet exhibits slight stretching and is sized to accommodate a wrist circumference of up to 7 and 3/4 inches. The push-pieces, crown, and case back, which features factory engravings, are reported to be in satisfactory condition.

The described condition represents the current state as reported by the selling entity.

Evidence for this section
  • “ساعت بر روی بند فولادی فابریک سیکو ارائه شده که طبق منبع دارای کشش خفیف بوده”
  • “این ساعت فاقد هرگونه لوازم جانبی اضافی و جعبه یا مدارک اولیه است”

Open research questions

  • Does the movement serial number confirm a 1971 production date?
  • What are the specific mathematical functions supported by the 6138-7000 slide rule bezel?

Source evidence

Recorded claims and source quotations for Seiko Calculator Chronograph 6138-7000
FieldSource-reported valueSource quotation
MakerSeiko“سازنده ژاپنی”
ModelCalculator Chronograph“با عنوان ماشین‌حساب (Calculator) شناخته می‌شود”
Reference6138-7000“مدل 6138-7000”
Date1971“سال ۱۹۷۱”
MovementSeiko Cal. 6138“مجهز به کالیبر اتوماتیک 6138 سیکو”
Case MaterialStainless steel“قاب فولادی ضدزنگ”
Case Diameter45 mm“قطر ۴۵ میلی‌متر”
BraceletOriginal Seiko steel“بند فولادی فابریک سیکو”

Visible details

  • Slide rule bezel with secondary transparent plastic indicator
  • Matte black dial with metallic grey sub-registers
  • Orange chronograph hands
  • Seiko automatic Caliber 6138 movement

Research qualifications

  • The exact state of the movement's long-term accuracy is not verified by this site
  • The authenticity of individual internal components is not independently confirmed

Photograph identity and source facts were screened before import; rights clearance remains pending.

Consulted source

ساعت مچی Seiko Calculator Chronograph مدل 6138-7000 سال 1971

Reviewed 2026-11-02 · Record 2d45c77339

Terms in this record

Glossary explanations for terms named in this object’s record.

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