Watches Seiko Filed Oct 11, 2026 by Joe
Seiko Prospex Alpinist SPB121
The Seiko Prospex Alpinist SPB121 is a Japan-made 39.5 mm automatic, 87 g, 200 m, with a rotating compass ring. Caliber 6R35, about 70 hours.
Worth it if
- You want 200 m, a date, and a compass ring on a green Alpinist dial.
Skip it if
- You want titanium or a longer power reserve. That is the Hamilton.
Specifications
| Reference | SPB121 (SPB121J1) |
| Case | 39.5 mm stainless steel. 13.2 mm thick. 46.4 mm lug-to-lug. Japan-made |
| Crystal | Sapphire with magnifier. Anti-reflective coating on the inner surface |
| Movement | Caliber 6R35 automatic with manual winding. About 70 hours. +25 to −15 seconds per day |
| Water resistance | 20 bar (200 m) |
| Features | Rotating compass inner ring. Date. Screw-down crown. See-through case back |
| Weight | 87.0 g |
| Origin | Japan |
Source: Seiko USA warranty
NotesJoe
The Seiko Prospex Alpinist SPB121 is the green compass watch. Japan-made. 39.5 mm steel. 13.2 mm thick. 46.4 mm lug-to-lug. 87.0 g. Sapphire with a cyclops and inner AR. 6R35. About 70 hours. +25 to −15 seconds a day. 200 m. Date. Rotating compass inner ring. Screw-down crown. Exhibition back.
Seiko Alpinist SPB121 notes
No prices. No Amazon. Official Seiko page only. Authorized-dealer warranty.
Hamilton Khaki Field Titanium Automatic is the titanium Swiss sibling. Hamilton Khaki Field vs Seiko Alpinist is the ledger.
Questions
What movement is in the SPB121?
Caliber 6R35, automatic with manual winding. About 70 hours. Stated accuracy +25 to −15 seconds per day.
What is the warranty?
Seiko USA is three years from purchase from Seiko or an authorized dealer. No Amazon link on this page.
