Seiko · Prospex Sea and Prospex LX line

Seiko SLA061J1 vs Seiko SNR029J1

15 published specifications differ between these two, and 2 are identical. Every figure below is what the manufacturer states for that reference; nothing is inferred from the other watch.

What differs

Specification	Seiko 1970 Heritage Diver's Black Series Limited Edition, 8L35SLA061J1	Seiko LX line Spring Drive diver, 5R65, titaniumSNR029J1
Case	Stainless steel with hard coating, 44.0 mm	Titanium with super-hard coating, 44.8 mm
Diameter	44 mm	44.8 mm
Thickness	13 mm	15.7 mm
Lug to lug	49.3 mm	50.9 mm
Lug width	20 mm	22 mm
Water resistance	200m / 660ft diver's	300m / 1000ft for saturation diving
Crystal	Curved sapphire crystal, anti-reflective coating on inner surface	Sapphire crystal, anti-reflective coating on inner surface
Case back	Screw case back, engraved LIMITED EDITION and serial number	Screw case back
Bracelet	Bracelet length 200.0 mm, 20 mm between the lugs; an additional silicone strap is included	22 mm between the lugs
Clasp	Three-fold clasp with secure lock, push button release with extender	Three-fold clasp with secure lock and push button release, solid and slide adjuster
Calibre	8L35	5R65
Movement	Automatic with manual winding	Spring Drive
Power reserve	Approximately 50 hours	Approximately 72 hours (3 days)
Jewels	26	30
Movement notes	Precision stated as +15 to −10 seconds per day. Stop second hand function and date display. Total weight 185.0 g. Limited edition of 1,000 pieces.	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.

What is identical

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

Bezel: Unidirectional rotating bezel
Crown: Screw-down crown

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.

Frequency	28,800 vibrations per hour (8 beats per second)	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.

One of these is the harder fit

Lug to lug is 50.9 mm on the SNR029J1 against 49.3 mm on the SLA061J1 — a 1.6 mm difference across the wrist. Diameter is what buyers ask about; lug to lug is what decides whether a case sits flat or overhangs. Ask for a wrist measurement before shipping the SNR029J1, and put the figure in the listing rather than the diameter alone.

A visible difference in how they wear

2.7 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 200 on the SLA061J1. 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.

Two different ownership conversations

The SLA061J1 is self-winding and the SNR029J1 is Spring Drive. 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.

One survives the weekend and one does not

72 hours on the SNR029J1 against 50 on the SLA061J1. Below about sixty hours a watch left off the wrist from Friday is stopped by Monday. Wind both fully at intake and confirm they reach the stated figure — a short reserve leaves a tired barrel nowhere to hide, and it is the kind of fault a buyer reports in week two.

Different case materials, different handling

The SLA061J1 is steel and the SNR029J1 is titanium. Different case materials mark, polish and refinish differently, so the condition language that fits one will mislead on the other. Photograph and describe each on its own terms.

What to check on each

SLA061J1

Hold this movement to its own tolerance of +15 to −10 seconds a day, which is materially tighter than the +25 to −15 published for the 6R calibres. A watch that would pass on a 6R may fail here.
Expect approximately 50 hours, not seventy. The 8L35 has the shortest reserve of the Seiko references documented here, and a weekend off the wrist will stop it.
Confirm the additional silicone strap is present. Seiko lists it as part of what ships with the watch, so a missing strap is an incomplete set rather than an optional extra.

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.

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.