The Seiko Prospex SPB377 and SPB379 are the blue- and black-dial versions, respectively, of Seiko’s Alpinist Mechanical GMT. Their official specifications are otherwise shared: each has a 6R54 automatic GMT movement, a compass-marked inner ring, a 39.5 mm steel case and 20 bar water resistance. Seiko’s US product pages list both at $1,150; choose between them primarily by dial color and preferred strap.
What is the difference between the SPB377 and SPB379?
The difference established by Seiko’s product pages is the dial color: the SPB377J1 is blue, while the SPB379J1 is black. Both are Prospex Mechanical GMT watches, not diver references. Seiko does not specify a technical-performance difference between the two.
| Reference | Dial | Band | US listed price |
|---|---|---|---|
| SPB377J1 | Blue | Cow leather | USD 1,150 |
| SPB379J1 | Black | Cow leather | USD 1,150 |
Prices are those shown on Seiko Watch Corporation’s US product pages, accessed in 2026, and may change. Regional prices and availability can differ; the US listing does not establish what either watch costs or whether it is in stock elsewhere.
What do the SPB377 and SPB379 have in common?
6R54 automatic GMT movement
Each watch uses Seiko caliber 6R54, with automatic and manual winding, a 24-hour hand for dual-time display, a stop-seconds function, 24 jewels and a stated accuracy range of +25 to -15 seconds per day. Seiko specifies approximately 72 hours (three days) of power reserve. Seiko describes it as: “The new Caliber 6R54, which has a power reserve of three full days, powers the new Seiko Prospex Alpinist Mechanical GMT.”
Case, crystal and water resistance
Both have a stainless-steel case with super-hard coating, a curved sapphire crystal with anti-reflective coating on its inner surface, and a screw-down crown. The case measures 39.5 mm in diameter, 13.6 mm thick and 46.4 mm from lug to lug. Seiko rates each watch for 20 bar water resistance.
That water-resistance rating is a specification, not a claim that the watch is a diver model. These references are described as Mechanical GMT watches and also include a rotating compass inner ring.
Rank #2
- Timeless Design: Crafted with a classic, round case and a green dial featuring a crosshair pattern, this Seiko Prospex Alpinist watch exudes timeless appeal
- Durable Construction: Built to last with a robust stainless steel case and scratch-resistant sapphire crystal, ensuring long-lasting wear
- Automatic Movement: Powered by Seiko's renowned automatic Caliber 6R35 movement, offering a 70-hour power reserve
- Compass Functionality: Equipped with a rotating compass inner ring, making it an ideal companion for outdoor adventures
- Water Resistance: Designed for water sports and swimming with a 200-meter water resistance rating, providing peace of mind during aquatic activities
Dial details and strap
Both models have LumiBrite and a rotating compass inner ring. Each comes on a cow-leather band with a three-fold clasp and push-button release; the lug width is 20 mm. A different strap may be an option if its fit and compatibility are confirmed, but the listed supplied band is leather on both references.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Which one should you choose?
- Choose the SPB377J1 if you prefer the blue dial.
- Choose the SPB379J1 if you prefer the black dial.
- Compare locally before buying if price or stock is decisive: the $1,150 figure is Seiko’s US listing, not a guaranteed price in other regions or at every retailer.
- Check the strap before ordering if you want a different material or style. Both listed versions use a 20 mm cow-leather band, and strap fit should be confirmed for the watch and replacement band.
For practical use, the shared 24-hour hand provides a dual-time display, while the compass inner ring adds a directional reference. Sapphire crystal, 20 bar water resistance and the screw-down crown are also common to both. Those shared features do not distinguish one reference’s performance from the other.
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Quick Recap
Best Value
- STAINLESS STEEL CASE built to endure with style, making this watch your perfect daily companion
- AUTOMATIC MOVEMENT for seamless precision in every tick of this watch
- SCRATCH-RESISTANT CRYSTAL to maintain a pristine look even with daily wear and tear on your watch
- LUMINESCENT HANDS for effortless readability in low-light conditions, ensuring you never miss a moment with this watch
- WATER RESISTANT DESIGN ensuring your watch is ready for any adventure, rain or shine
Rank #4
- DAY/DATE CALENDAR: stay organized with the convenient day/date calendar displayed on the beautiful blue dial
- STURDY STAINLESS STEEL CASE: designed for durability, this men's watch features a stainless steel watch case that can withstand everyday wear and tear SEIKO QUALITY: handcrafted timepieces for every occasion
- CLASSIC BROWN LEATHER STRAP: the combined sophistication and versatility of a supple leather watch band make these the perfect men’s watches for any occasion
- 50M WATER RESISTANT: whether you're washing your hands or snorkeling off the coast, these men's wrist watches are water-resistant up to 50 meters, providing peace of mind in any situation
- SMOOTH AUTOMATIC MOVEMENT: our self-winding automatic watches for men deliver precise and smooth movement, ensuring accurate timekeeping LUMINOUS HANDS AND MARKERS: even in low light conditions, the luminous hands and markers ensure that you can read the dial indicator
Rank #3
- Screw-down crown, screw, see-through caseback, 70 hour power reserve, magnified date window, LumiBrite hands and markers
Official specifications and product pages
| Specification | SPB377J1 and SPB379J1 |
|---|---|
| Movement | Seiko caliber 6R54; automatic with manual winding |
| Accuracy | +25 to -15 seconds per day |
| Power reserve | Approximately 72 hours (3 days) |
| Jewels and functions | 24 jewels; 24-hour dual-time hand; stop-seconds function |
| Case | Stainless steel with super-hard coating; 39.5 mm diameter; 13.6 mm thickness; 46.4 mm lug-to-lug |
| Crystal | Curved sapphire; anti-reflective coating on inner surface |
| Water resistance | 20 bar |
| Band and lug width | Cow leather; three-fold clasp with push-button release; 20 mm |
| Other features | LumiBrite; rotating compass inner ring; screw-down crown; see-through screw case back |
Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon at the time of purchase will apply.
