When two master craftsmen collide. In 1996, two of Seiko’s most decorated employees created a watch that shaped the future of Japanese haute horlogerie.
That watch in question was the Credor GBBD987 - a skeletonised dress piece in solid platinum, housing the razor-thin 6899 calibre. Mamoru Sakurada designed, built, and assembled the movement, while Kiyoshi Terui engraved every available millimetre by hand. To them, it was more than just a watch - it was a signal to the watch world that Seiko was upping its game.
A few years later, in 2004, Sakurada and Terui would become two of the three founding members of the now-famous Shizukuishi Watch Studio - the birthplace of all mechanical Grand Seikos and select Credors. Today, they’re often considered to be two of the greatest artisans in Seiko’s modern history, and this watch has the distinct honour of being their first known partnership.
Remarkably, both men worked well into their golden years. Sakurada joined Seiko in 1965, and while I’m not able to find official confirmation of his retirement, in the mid-2010s a handful of 68-series movements emerged bearing his engraved signature. This was first time he signed his assembly work, so it seems sensible to view these as his farewell.
Terui, meanwhile, is still engraving in his 70s. His most recent project, the GBBY975 “Goldfeather”, proves that age hasn’t dulled his touch - nor his relevance.
Their work on the 6899 series remains a technical benchmark. Assembling the movement was a reactive process for Sakurada - piece by piece, each component is shaped and fitted on the fly against the one that came before it. Tolerances of 0.03mm are judged by touch alone.
Sakurada’s protégé, Katsuo Saito, spent five years under his tutelage before he was trusted with a full build. And today, Saito himself has been training his own successor for four years.
Terui’s standards are no less punishing. While the calibre itself is only 1.98mm thick, some sections are as thin as 0.25mm. In order to maintain structural integrity, he works to a maximum engraving depth of 0.15mm – all checked by his touch, with a sensitivity refined over decades. His successor, Tsune Ogawa, trained for four years before earning the right to put his mark on a real 68 movement.
For these achievements, both men were awarded the Yellow Ribbon - a rare distinction granted by the Japanese Government to individuals whose mastery of an industry is considered irreplaceable.
And yet, for all its technical brilliance, the GBBD987 remains poetic. Its skeletonised bridges were shaped to resemble bamboo stalks swaying in the wind, and Terui’s engravings feature traditional Japanese motifs, including the Chrysanthemum flower - the Imperial Seal of Japan. The case, made from 950 platinum, carries unexpected heft for such a modestly sized dress watch, grounding it with quiet power.
The result is not just a rare Credor, or an early example of the 6899. It’s a deeply Japanese artifact - humble in scale, immense in meaning, and rooted in the lives of two master craftsmen at the start of a shared journey that altered the trajectory of Seiko forever.