Jiro Matsumoto

Japanese Watchmaking Editor

Jiro covers Seiko, Grand Seiko, Citizen, Credor and independent Japanese makers like Hajime Asaoka. Based in Tokyo with full industry access.

Articles by Jiro Matsumoto (6)

grand-seiko

Spring Drive's Tri-synchro Regulator: Why No Swiss Maker Copied It

Spring Drive's tri-synchro regulator achieved unprecedented accuracy 25 years ago. Why hasn't a single Swiss manufacture copied this proven hybrid regulation system?

April 26, 2026

grand-seiko

Grand Seiko SBGW231's Case Geometry: When Zaratsu Creates Optical Illusions

Why Grand Seiko's zaratsu polishing creates distortion-free reflections that cameras can't capture—a forensic analysis of the SBGW231's optical geometry.

April 22, 2026

grand-seiko

Spring Drive's Tri-synchro Regulator: Why No Swiss Brand Replicates It

Spring Drive's electromagnetic brake requires vertical integration from quartz oscillators to IC fabrication—a manufacturing structure no Swiss brand possesses.

April 22, 2026

citizen

Why Citizen's Chronomaster AB9000 Challenges Swiss ±5 Precision

Citizen's Caliber 0200 achieves ±5 seconds/year accuracy through pure mechanical watchmaking. We examine the 800-component twin barrel system that challenges Grand Seiko without electronics.

April 18, 2026

grand-seiko

Grand Seiko's Hidden Watchmaking Schools: Shizukuishi & Micro Artist

Shizukuishi Watch Studio and Micro Artist Studio produce fundamentally different Grand Seiko watches. Geographic isolation and craftsmen traditions explain why.

April 18, 2026

Spring Drive vs Swiss Co-Axial: Why Two Friction Solutions Diverged

Grand Seiko's Spring Drive eliminates the escapement entirely while Omega's Co-Axial perfects it. Two philosophies, one problem: friction in mechanical timekeeping.

April 18, 2026