Seiko - Railway-Issued Precision Sub-seconds Diaflex - 1950-1959

Introduction

This is a Seiko Precision open-face pocket watch with a crisp white dial carrying bold Arabic numerals, blued steel hands, and a subsidiary seconds register at the 6 o'clock position inscribed 'SECOND SETTING DIAFLEX'. The movement is manual winding, signed SEIKOSHA on the plate. The exterior caseback is stamped with Japanese characters indicating a supply number and issuing organisation, identifying this as a formally issued timepiece.

Historical / Era context

The DIAFLEX inscription refers to Seiko's shock-resistant Diaflex mainspring, introduced in the mid-20th century to improve reliability under daily working conditions. The exterior caseback carries the stamped characters 国 and 鉄, which together form 国鉄 — the abbreviation for Japanese National Railways (JNR) — alongside what reads as 昭 30 and supply number 10372, indicating this watch was issued in 1955 by the national railway organisation. The movement plate, signed SEIKOSHA, is finished with striated Geneva-style striping and a visible ruby jewel at the pallet fork, consistent with the high-grade finishing applied to JNR-contracted watches.

Condition

The watch is running, with a measured rate of approximately +45 seconds per day (gaining). The watch was checked lying flat (dial up) after a full wind. This is a spot check at the time of listing; as a vintage mechanical watch the rate in actual wear varies with position and winding state, and long-term accuracy is not guaranteed. As a vintage timepiece it may benefit from a service.

Case: The chrome-plated case shows clear signs of wear in service: scattered rust spotting and plating loss is visible on the bezel rim, the mid-band, and the caseback exterior, particularly concentrated at the lower right quadrant of the case band. The bow and crown retain good detail. The caseback opens to reveal a well-preserved movement. Overall the case presents honest working patina consistent with its age and institutional use.

Dial: The white dial is clean and fully legible, with no cracks, significant staining, or damage visible. The bold Arabic numerals and all printed text — including the subsidiary seconds ring markings — are sharp and intact. The blued hands show no notable damage.

Crystal: The crystal is present and the dial is clearly readable through it. There is light surface wear consistent with age, but no cracks or deep scratches are visible.

Movement: The watch is running. With the caseback opened, the SEIKOSHA-signed movement is visible, displaying attractive striated finishing on the mainplate and bridges, a gold-coloured centre wheel, a ruby jewel at the pallet fork, and a regulation index marked F and S. The keyless winding and setting action functions normally.

Accessories: No box, papers, chain, or additional accessories are included.

Please review all photographs carefully for the detailed condition.

Specifications

Brand: Seiko
Model: Seiko Precision
Movement: Manual winding mechanical movement
Case material: Chromed
Case diameter: approx. 49.9 mm
Total length including crown: approx. 61.3 mm
Total length including crown and ring: approx. 66.4 mm
Dial color: White
Period: 1950-1959
Weight: approx. 86 g
Accessories: None (watch only)
In working order: Yes
Timekeeping: approx. +45 seconds per day (checked lying flat after a full wind)

Closing note

A genuine JNR-issued Seiko Precision pocket watch from 1955, combining institutional provenance, a beautifully finished Seikosha movement, and the iconic Diaflex mainspring — a highly desirable piece for collectors of Japanese railway horology. Please examine all photographs carefully as they form part of the description.
As with all vintage timepieces, please examine the provided photographs carefully to satisfy yourself with the condition before bidding. The watch is sold as a vintage collectible; water resistance and future maintenance are not guaranteed.
The item is carefully packed and shipped from Japan with tracking.
Import duties, taxes and customs charges are the buyer's responsibility.