This timepiece is a magnificent artifact from the Japanese Domestic Market (JDM), representing the elite Chronometer Officially Certified line of the King Seiko family. The reference 5625-7040 is defined by its stunning charcoal grey sunburst dial, a rare and highly sought-after variant that provides a sophisticated, moody contrast to the sharp stainless steel furniture. It is powered by the legendary Caliber 5625A, a high-frequency $28,800 \text{ bph}$ automatic engine that was designed to meet and exceed stringent chronometer standards. This movement is a mechanical masterpiece, featuring a high-beat sweep seconds hand and a quick-set date function, all housed in a beautifully finished slim profile.
The architecture of this watch is a pure expression of Seiko's "Grammar of Design," featuring razor-sharp lug transitions and a high-polish finish that creates a brilliant play of light. The most prestigious feature is found on the caseback: the original gold KS Chronometer medallion, which remains in excellent condition—a definitive hallmark of a high-tier Seiko that was never meant for the average consumer. The dial is further distinguished by its applied "KS" logo and the "Officially Certified" text, a rare branding that Seiko eventually moved away from in later years. The caseback reveals the serial number 251038, definitively dating this specimen to May 1972. This is an essential acquisition for an elite collector who appreciates Suwa factory excellence, rare dark-dial JDM variants, and the absolute peak of 1970s Seiko precision.
