Seiko · Prospex Land and Prospex Sea
Seiko SPB379J1 vs Seiko SPB453J1
10 published specifications differ between these two, and 7 are identical. Every figure below is what the manufacturer states for that reference; nothing is inferred from the other watch.
What differs
| Specification | ||
|---|---|---|
| Case | Stainless steel with super hard coating, 39.5 mm | Stainless steel, 40.0 mm |
| Diameter | 39.5 mm | 40 mm |
| Thickness | 13.6 mm | 13 mm |
| Water resistance | 20 bar | 300m / 1000ft diver's |
| Bezel | Rotating compass inner ring | Unidirectional rotating bezel |
| Case back | See-through and screw case back | Screw case back |
| Bracelet | Cow leather band, 20 mm between the lugs | 20 mm between the lugs |
| Clasp | Three-fold clasp with push button release | Three-fold clasp with secure lock, push button release with extender |
| Calibre | 6R54 | 6R55 |
| Movement notes | Precision stated as +25 to −15 seconds per day. 24-hour hand for dual time display, stop second hand function. Magnetic resistance 4,800 A/m. LumiBrite on hands and indexes. | Precision stated as +25 to −15 seconds per day. Stop second hand function. LumiBrite on hands, indexes and bezel. Total weight 168.0 g. |
What is identical
Worth knowing as much as the differences: these are the specifications you cannot use to tell the two apart.
- Lug to lug
- 46.4 mm
- Lug width
- 20 mm
- Crystal
- Curved sapphire crystal, anti-reflective coating on inner surface
- Crown
- Screw-down crown
- Movement
- Automatic with manual winding
- Power reserve
- Approximately 72 hours (3 days)
- Jewels
- 24
What the differences cost you
Each note below follows from the published figures in the tables above — what they mean for intake, for a listing, and for the handover. Nothing here estimates a price or a margin.
Do not describe these the same way
300 metres on the SPB453J1 against 200 on the SPB379J1. Both are more than daily life asks for, so the number is a listing-accuracy question rather than a practical one: quote each watch its own figure, and remember that neither rating survives an unserviced case by itself.
Different movements to verify and to service
The SPB379J1 runs the 6R54 and the SPB453J1 the 6R55. Two consequences at intake: the service history that is normal for one calibre is not evidence about the other, and the calibre is the check that catches a movement swapped into the wrong case. Confirm the movement matches the reference rather than assuming it from the dial.
What to check on each
SPB379J1
- Turn the inner compass ring through a full revolution using its own crown and confirm it moves smoothly and holds position. It is driven from a second crown, so a seized ring is a crown or pinion problem rather than something you can free by hand.
- Note the water resistance is given as 20 bar, not as a diver's rating. This is a Prospex on a leather band and it should not be described in the language Seiko reserves for its dive watches.
- Check both crowns screw down. There are two penetrations of the case here and the one for the inner ring is the one owners forget to secure.
SPB453J1
- Read the published precision before you time one. Seiko states +25 to −15 seconds per day, so an example gaining twenty seconds daily is inside its own specification and is not a fault to price around.
- Test the clasp extender as well as the clasp. It is a moving part with its own catch, it is used over a wetsuit, and it is the component most likely to have been bent.
- Turn the bezel anticlockwise through a full revolution and confirm it will not move the other way at all. A unidirectional bezel that turns both ways has lost its safety function.
Sources
- Seiko official product page for reference SPB379J1 (Prospex Land, Alpinist Mechanical GMT) - Caliber Number: 6R54; Movement Type: Automatic with manual winding; Precision: +25 to -15 seconds per day; Power reserve: Approx. 72 hours(3 days); Jewels: 24; Case Material: Stainless steel (super hard coating); Case Size: Thickness:13.6mm; Diameter:39.5mm; Lug-to-lug:46.4mm; Crystal: Curved sapphire crystal; Crystal Coating: Anti-reflective coating on inner surface; LumiBrite: LumiBrite on hands and index(es); Band Material: Cow leather; Clasp: Three-fold clasp with push button release; Distance between lugs: 20; Water Resistance: 20 bar; Magnetic Resistance: 4,800 A/m; Functions: 24-hour hand (dual time display function); Stop second hand function; Features: Rotating compass inner ring; Screw-down crown; See-through & Screw case back — retrieved 2026-09-22
- Seiko official product page for reference SPB453J1 (Prospex Sea, 1965 Heritage Diver's Watch) - Caliber Number: 6R55; Movement Type: Automatic with manual winding; Precision: +25 to -15 seconds per day; Power reserve: Approx. 72 hours(3 days); Jewels: 24; Case Material: Stainless steel; Case Size: Thickness:13.0mm; Diameter:40.0mm; Lug-to-lug:46.4mm; Crystal: Curved sapphire crystal; Crystal Coating: Anti-reflective coating on inner surface; LumiBrite: LumiBrite on hands, index(es) and bezel; Clasp: Three-fold clasp with secure lock , push button release with extender; Distance between lugs: 20; Water Resistance: 300m / 1000ft diver's; Weight: 168.0g; Functions: Stop second hand function; Features: Unidirectional rotating bezel; Screw-down crown; Screw case back — retrieved 2026-09-22
Not affiliated with Seiko. Specifications are read from each manufacturer's own published documentation on the dates shown and may change; the manufacturer's current documentation governs.