Seiko · Prospex LX line and Astron

Seiko SNR029J1 vs Seiko SSH151J1

14 published specifications differ between these two, and 1 are identical. Every figure below is what the manufacturer states for that reference; nothing is inferred from the other watch.

What differs

Specification	Seiko LX line Spring Drive diver, 5R65, titaniumSNR029J1	Seiko Astron GPS Solar 5X83, titanium with ceramic bezelSSH151J1
Case	Titanium with super-hard coating, 44.8 mm	Titanium with ceramic and titanium bezel, 43.3 mm
Diameter	44.8 mm	43.3 mm
Thickness	15.7 mm	13.4 mm
Lug to lug	50.9 mm	49.5 mm
Water resistance	300m / 1000ft for saturation diving	10 bar
Crystal	Sapphire crystal, anti-reflective coating on inner surface	Dual-curved sapphire crystal, super-clear coating
Bezel	Unidirectional rotating bezel	Ceramic and titanium
Bracelet	22 mm between the lugs	Titanium; Seiko publishes a distance between lugs of 14 mm for this reference, which does not sit easily with the 43.3 mm case and should be measured before ordering parts
Clasp	Three-fold clasp with secure lock and push button release, solid and slide adjuster	Easy-adjust three-fold clasp with push button release
Calibre	5R65	5X83
Movement	Spring Drive	GPS solar
Power reserve	Approximately 72 hours (3 days)	Operating for approximately 6 months when fully charged; power save approximately 2 years
Jewels	30	14
Movement notes	Precision stated as ±15 seconds per month (±1 second per day). Power reserve indicator, stop second hand function and date display. LumiBrite on hands and indexes. Total weight 162.0 g.	Precision stated as ±15 seconds per month without receiving a GPS signal, at temperatures between 5°C and 35°C. Perpetual calendar to 28 February 2100, world time for 38 cities, dual time, chronograph to 12 hours in 1/20 second increments, power reserve indicator, DST, in-flight mode, automatic hand position alignment. Listed as allergy-safe metal. Magnetic resistance 4,800 A/m. Total weight 117.0 g.

What is identical

Worth knowing as much as the differences: these are the specifications you cannot use to tell the two apart.

Case back: Screw case back

Stated for one, not the other

These rows cannot be compared, because one maker publishes the figure and the other does not. An empty cell is a gap in the manufacturer's documentation, not a gap in the watch — and not a licence to fill it in from the other column.

Lug width	22 mm	not stated
Crown	Screw-down crown	not stated

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.

A visible difference in how they wear

2.3 mm of thickness separates these, with the SNR029J1 the taller at 15.7 mm. That is the difference between a watch that goes under a cuff and one that catches on it — worth a photograph from the side rather than a number in a table.

Do not describe these the same way

300 metres on the SNR029J1 against 100 on the SSH151J1 — not a variation on the same watch but a different class of one, built around a case and crystal designed for depth. Expect different buyers, different questions, and a different service conversation. Never carry the SNR029J1's rating into the SSH151J1's listing.

Two different ownership conversations

The SNR029J1 is Spring Drive and the SSH151J1 is solar. That changes what a buyer needs telling at handover, and it changes intake: a hand-wound watch has no rotor to mask a tired mainspring, and a stopped quartz watch is usually a battery rather than a fault.

Different movements to verify and to service

The SNR029J1 runs the 5R65 and the SSH151J1 the 5X83. 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

SNR029J1

Watch the seconds hand sweep without stopping for ten seconds. This is Spring Drive under the Seiko name rather than the Grand Seiko name, and the glide is the first thing that confirms the movement is what the reference claims.
Read the water resistance exactly: it is stated as 300m for saturation diving, which is a different and higher claim than a plain 300m diver's rating.
Use the dial's power reserve indicator to audit the 72-hour figure over a day, then check the slide adjuster in the clasp moves and locks.

SSH151J1

Charge it in daylight and then trigger a GPS reception before you judge anything. A solar watch that has sat in a drawer or a dark safe will behave badly until it has been charged, and that is not a fault.
Run the automatic hand position alignment function. Hands that have drifted out of alignment make every other function read wrong, and the watch has a routine to correct it.
Confirm the in-flight mode can be entered and cleared. It suppresses GPS reception, and a watch left in it will appear to have lost its ability to find a signal.

Sources

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.