Grand Seiko against Rolex

Grand Seiko SLGH005 vs Rolex 124270

13 published specifications differ between these two. Every figure below is what the manufacturer states for that reference; nothing is inferred from the other watch.

What differs

Specification	Grand Seiko Hi-Beat 36000 80 Hours, stainless steelSLGH005	Rolex Explorer 36mm, Oystersteel124270
Case	Stainless steel, 40.0 mm	Oyster, 36 mm, Oystersteel. Monobloc middle case, screw-down case back and winding crown
Diameter	40 mm	36 mm
Water resistance	10 bar	Waterproof to 100 metres / 330 feet
Crystal	Box shaped sapphire crystal, anti-reflective coating on inner surface	Scratch-resistant sapphire
Dial	Described as silvery white with an intricate pattern expressing the white birch forests near Grand Seiko Studio Shizukuishi	Black, with highly legible Chromalight display with long-lasting blue luminescence
Case back	See-through and screw case back	Screw-down
Crown	Screw-down	Screw-down, Twinlock double waterproofness system
Bracelet	22 mm band width, 190 mm band perimeter	Oyster, three-piece solid links, Oystersteel
Clasp	Folding clasp with push button release	Folding Oysterlock safety clasp with Easylink 5 mm comfort extension link
Calibre	9SA5	Calibre 3230, Manufacture Rolex
Movement	Self-winding with manual-winding	Perpetual, mechanical, self-winding; bidirectional self-winding via Perpetual rotor
Power reserve	Approximately 80 hours	Approximately 70 hours
Movement notes	Mean daily rate +5 to −3 seconds per day; normal usage accuracy +8 to −1 seconds per day. Described as a Grand Seiko-exclusive automatic movement with a Dual Impulse Escapement and twin barrels. Total weight 178 g.	Precision −2/+2 sec/day after casing. Centre hour, minute and seconds hands with stop-seconds; no date. Paramagnetic blue Parachrom hairspring with Paraflex shock absorbers.

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.

Thickness	11.7 mm	not stated
Lug to lug	47 mm	not stated
Lug width	22 mm	not stated
Bezel	not stated	Smooth
Frequency	36,000 vibrations per hour	not stated
Certification	not stated	Superlative Chronometer (official chronometer certification + Rolex certification after casing)

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.

You will have to measure one of these

Lug to lug is published for the SLGH005 but not for the 124270. It is the figure that actually predicts fit, so measure the 124270 yourself with callipers and say in the listing that the number is your own measurement, not the maker's.

These reach different buyers

40 mm on the SLGH005 against 36 mm on the 124270. Diameter is a poor predictor of how a watch actually sits, but it is the field buyers filter on, so the two land in front of different people. Do not let one listing's photographs or copy stand in for the other.

Different movements to verify and to service

The SLGH005 runs the 9SA5 and the 124270 the Calibre 3230, Manufacture Rolex. 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

SLGH005

Time it over a full day against the two published figures. Grand Seiko gives a mean daily rate and a separate normal usage accuracy, so judge a worn watch against the wider of the two rather than the laboratory number.
Study the box crystal from a low angle for chips at the edge where the glass turns down. A box profile stands proud of the case, takes knocks the bezel would otherwise absorb, and is an expensive part to replace.
Ask when it was last serviced and treat a vague answer seriously. A movement beating 36,000 times an hour puts more cycles through its parts in a year than a slower one does, whatever its reserve.

124270

Put almost all your attention on the case. With no bezel insert, no date and no complication, condition and originality of the steel is most of what distinguishes one example from another.
Check the crown is the Twinlock system rather than Triplock. This reference uses the two-seal crown, and knowing which you are looking at matters when assessing a case that has been apart.
Sight along the polished lug chamfers. At 36mm there is little material to lose, and a refinished case shows in softened bevels long before it shows anywhere else.

Sources

Not affiliated with Grand Seiko or Rolex. Specifications are read from each manufacturer's own published documentation on the dates shown and may change; the manufacturer's current documentation governs.