The Grand Seiko SBGM021 is a discontinued automatic GMT with a traditional ivory dial, blue 24-hour hand, and 39.5 mm polished steel case. Its caliber 9S66 displays a second time zone and is specified for approximately 72 hours of power reserve. The dimensions and design below are specific to the SBGM021 where identified; current SBGM221 data is used only as related-model context.
What the SBGM021’s GMT hand does
The SBGM021 uses an additional 24-hour hand to show a second time zone alongside the main time display. In practice, set that hand against the 24-hour scale to track another location’s time, including whether it is day or night there. Grand Seiko describes the 9S66 GMT as a second-time-zone display; the available reference information does not establish independently jumping local-hour behavior.
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The exact-reference retailer archive also lists calendar-linked time-difference adjustment and a stop-seconds function. The latter lets the seconds hand stop when setting the time. These features complement the watch’s conventional mechanical time display rather than turning it into a digital or independently adjusted world-time watch.
Design: restrained dress-watch styling
Dial and display
Fratello’s SBGM021 review describes an ivory dial with applied, polished markers, a framed date aperture, and a blue GMT hand. The contrast makes the second-time-zone hand easy to distinguish visually without changing the otherwise classical layout. The dial color and details here refer to the SBGM021 review; Grand Seiko’s description of a “porcelain-like” dial texture is for the related SBGM221 and should not be assumed to verify the SBGM021’s surface finish.
#1 Best Overall
- Three-fold clasp with push button release
- Dual-curved sapphire crystal
- Power reserve display on the back
- Power resrve Approx. 72 hours(3 days)
Case, crystal, and strap
The review identifies a polished stainless-steel case, box-shaped sapphire crystal, sapphire display back, and brown alligator strap with a steel folding clasp. Its reported dimensions are 39.5 mm in diameter, 13.7 mm thick, and 19 mm between the lugs. Fratello’s reviewer called the polished facets striking and described the crown as easy to operate and the clasp as thin and comfortable; those are that reviewer’s impressions, not a separate fit test.
A 19 mm lug width gives owners a possible route to replacement straps, but width alone does not guarantee compatibility. Check the strap’s end shape, length, thickness, and clasp arrangement against the watch and your intended setup before ordering.
Caliber 9S66: reserve and accuracy specifications
The SBGM021 archive and Fratello review identify Grand Seiko caliber 9S66. It is an automatic mechanical movement with manual winding. Seiko’s official instructions specify a 24-hour hand, 28,800 vibrations per hour, and at least 72 hours of power reserve when the mainspring is sufficiently wound. Grand Seiko’s current SBGM221 page likewise gives approximately 72 hours for that related model.
Seiko lists a Grand Seiko Standard mean daily rate of -3 to +5 seconds per day for the 9S66 under controlled testing. That is a manufacturer specification, not a timing result for any particular SBGM021. Seiko cautions that actual mechanical-watch accuracy varies with temperature, position, use, and winding state; the SBGM221 page also gives a normal-use range of +10 to -1 seconds per day for that model.
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| Specification | SBGM021 detail | Evidence and qualification |
|---|---|---|
| Movement | Grand Seiko caliber 9S66; automatic with manual winding | Exact-reference archive and review identify the caliber; official Seiko instructions describe 9S66 |
| GMT display | 24-hour hand for a second time zone | Exact-reference archive and official related-model information |
| Power reserve | Approximately 72 hours; official instructions say 72 hours or more from a sufficiently wound mainspring | Published caliber specification, not an individual-watch test |
| Mean daily rate | -3 to +5 seconds per day | Grand Seiko Standard under controlled testing; daily results vary |
| Case diameter | 39.5 mm | Fratello’s exact-reference review; also listed for related SBGM221 |
| Thickness | 13.7 mm | Exact-reference review/archive |
| Weight | 88 g | Inoue Watch Store’s SBGM021 archive |
| Lug width | 19 mm | Fratello’s exact-reference review |
| Crystal and back | Box-shaped sapphire crystal; sapphire display back | Fratello’s exact-reference review |
| Strap | Brown alligator leather with folding clasp | Configuration described in Fratello’s review |
| Water resistance | Splash resistant / everyday-life water resistance | Available descriptions do not establish swimming or diving suitability |
How it is likely to wear—and what is not established
The 39.5 mm diameter and 13.7 mm thickness provide a useful starting point when comparing the SBGM021 with watches you already own. A 46.9 mm lug-to-lug figure appears on Grand Seiko’s current SBGM221 page, not in the exact-reference SBGM021 measurements cited here, so it should not be treated as a verified measurement for this watch. The reviewer’s comfort comments are subjective and do not substitute for trying a specific example on your wrist.
Rank #2
- Featuring a Black Band, Silver-tone Case, Scratch Resistant Hardlex Crystal
- Box-shaped Hardlex crystal
- Second hand halt mechanism (Hacking)
Water-resistance descriptions support treating it as a watch for everyday life and splashes, not as a swimming or diving choice. No stronger activity rating is established for the SBGM021 in the cited material.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Discontinued status and buying a pre-owned example
Inoue Watch Store’s archive says the SBGM021 was released in October 2010 and discontinued by 2023; when that archive statement was written, the retailer and Seiko showed no stock. This establishes the status in that archive’s context, not present-day worldwide availability. Current pre-owned inventory and market prices have not been established here, and historical prices from Fratello’s review are not current price guidance.
For a used example, assess the individual watch rather than relying on the model’s published specifications. Check condition, authenticity and provenance, included papers, service history, and the state of the strap and clasp. Ask for a recent timing or service assessment if available; the caliber’s published range alone cannot tell you how a particular watch is performing.
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Grand Seiko’s current SBGM221 page is useful context for the related 9S66 GMT design. It lists a 39.5 mm diameter, 46.9 mm lug-to-lug, 13.7 mm thickness, 19 mm band width, 88 g weight, splash resistance, and approximately 72-hour reserve. Those are SBGM221 page specifications and should not be silently transferred to an SBGM021 listing, except where the exact-reference review or archive independently supports the same value.
The SBGM221 page also describes its ivory-colored dial as having a lustrous, porcelain-like texture. That is manufacturer wording for the SBGM221, not an independently verified surface specification for the SBGM021.
Quick Recap
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