It has been exactly 30 years since Seiko revived its high-end line of automatic watches in 1992. Countless masterpieces have been created during this time. Among these iconic watches, Shiraichigo, a renowned watch collector, introduces some models that he particularly recommends.
Text by Shiroichigo
The revival of mechanical Grand Seiko
From the late 1980s to the early 90s, mechanical watches regained their place worldwide. Although Seiko reigned supreme in the quartz hierarchy, it had previously been a major player in the mechanical watch industry, and it could not sit idly by and watch the situation unfold. According to the Shizukuishi High-End Watch Workshop, which produces Grand Seiko mechanical models, in 88 it "restarted efforts to revive high-end mechanical watches after a 15-year hiatus." Then, in 91, to commemorate Seiko's 110th anniversary, it produced the Credor UTD (Ultra-Thin Dress) watch, featuring the ultra-thin 68 series movement, and began exploring a return to high-end mechanical watches.
Even at that time, Seiko continued to manufacture mechanical movements. However, these were mainly the 7000 series automatic movements used in the Seiko 5 and Mechanical Diver watches, which were manufactured for developing countries where batteries were difficult to obtain. The 7000 series movement was improved in the 1990s to become the 7S, and was subsequently further improved to develop into the 6R/4R, and remains an excellent and extremely important movement that supports Seiko's line of affordable mechanical watches to this day.
However, this movement was primarily practical, and it had some features that made it difficult to claim to be a luxury watch in terms of both appearance and precision, such as a nickel balance wheel and bridges with a rather unpractical finish. Therefore, Seiko set about developing a new movement in order to revive luxury mechanical watches.
However, at the time, Seiko's designers were focused on developing new quartz movements and could not allocate personnel to mechanical movements. Therefore, they attempted to unravel the old design drawings that had been preserved on microfilm and replace them with CAD data. However, the values and dimensions written on the old design drawings were often not applicable to the latest CAD data. They also had little know-how in developing new mechanical movements, so their first goal became to improve existing movements.
The base movement chosen was the 52 series movement, which was used in King Seiko watches in the 1970s. It has an 8-beat specification of 28,800 vibrations per hour, a calendar, and is 3.9 mm thick. It is a high-performance movement that was certified as a chronometer by the Japan Chronometer Certification Association at the time.
From "Grand Seiko: Ten Stories Spinning into the Future, Vol. 5: A Traditional Mechanical Watch Transcending Time, Part 1"
The completed model equipped with the Caliber 4S35 was released in 92. Seiko modestly described it as the first step in the revival of mechanical watches, but looking at the one I own, the actual watch is astonishingly meticulously crafted. The finish, particularly the thick, carefully printed minute and second indices on the dial, is still impressive even today (frankly, the finish of the second indices should be emulated in the new SLGH003). Using the Caliber 4S35 as a signal for its revival, Seiko attempted to further improve the precision of the 4S, resulting in the Caliber 4S79 for the Credor Chronometer, released in 98. The watch, limited to 500 pieces, was sent to Switzerland, where it was certified as a COSC chronometer and sold.
The 4S series calibers achieved excellent accuracy, but to achieve this high precision, it was necessary to use tricky techniques, like adding a weight to the balance spring (which at first glance looks like plastic dust and is often mistakenly removed during maintenance). Seiko had achieved a revival of the Grand Seiko brand with the success of its quartz models, but for Seiko, which places importance on the quality of the "framework" itself, the mechanical 4S series calibers were deemed insufficient for Grand Seiko.
For this reason, Seiko developed a new mechanical movement for Grand Seiko rather than improving on the 4S. This was the Caliber 9S55 movement, which was installed in the SBGR001 and 002 in 98. However, according to interviews with the developers, it seems that time was tight when developing the Caliber 9S55. It is said that the 3D-CAD developed by Seiko Instruments at the time proved to be a major help in this time crunch.
"We used past design documents to study the shape of the gears and simulate the wheel train, and then used this data to quickly create a prototype. A new regulator was also developed, and the shape of the hairspring also adopted a special inner curve, achieving the high precision worthy of the GS name."
From "Grand Seiko: Ten Stories Spinning into the Future, Vol. 5: A Traditional Mechanical Watch Transcending Time, Part 2"
The 9S55, which was released in this way, naturally inherited Seiko's previous mechanical lineage. The automatic winding mechanism was a pawl-winding Magic Lever, a system favored by Seiko. Some critics have described the 9S as an extended version of the 7S. However, I believe that rather than seeing it as an improved version of the 7S, Seiko made the most of the archives they had at the time, rather than developing it from scratch due to the short development timeframe, resulting in a mechanism that was similar.
For example, the regulator adjustment device was changed from the classic one found on the 7S to a specialized one with a spoon-shaped adjustment mechanism for tilt, which was extremely useful for adjusting isochronism. After the patent expired, the 7S adopted an etachron-style regulator, which allowed for tilt adjustment, but the 9S's regulator is more robust, as befits a luxury model. Also, while the 7S series' bridges are roughly finished because they emphasize practicality, the 9S features a beautiful wave pattern known as "Tokyo Wave." The stripe pattern is called Tokyo Wave and not Geneva Stripe because Japanese manufacturers use a different finish than Swiss models.
When creating the grain pattern, manufacturers in Switzerland and Germany use shallow grinding, while Japanese manufacturers use cutting, resulting in deeper grain. Up until then, Seiko had produced movements with a relatively plain finish, even for the 4S, which was aimed at a higher-end model than the 7S. For example, the manual-winding version of the 4S had grain on the bridges, but the rotor had a plain, radial finish. Therefore, the 9S, with its beautiful stripes all over, was a major improvement in terms of appearance, befitting a high-end watch.
The biggest change from the 4S35 to the 9S55 was not its appearance, but its thickness. Seiko thinned its movements when it transitioned from the 10-beat 61 series to the 8-beat 56 series. The 4S, chosen as a model for the revival of mechanical movements, was chosen in part because of its 4mm thinness. Indeed, its thinness allowed it to be used in many models, including the dressy Credor and Laurel. On the other hand, its thinness may have made it difficult to achieve the precision and stability required of Grand Seiko. Perhaps as an antithesis to the 4S, which required ingenuity to enhance precision, the Cal. 9S55 was a substantial movement, measuring 5.4mm thick for a diameter of 28.4mm.
