Seiko SSK001: specifications and what to check

Hardlex is a different material, and it changes your grading

Seiko fits three different crystal materials across the references documented on this site, and the difference matters enough to lead with.

Sapphire — on the Prospex and Presage references here. Extremely hard, so it essentially does not scratch. When it fails, it chips, and a chip means replacement.

Hardlex — this watch. Seiko's own hardened mineral glass. It is softer than sapphire and it does scratch, in ordinary use, from ordinary contact.

That inverts how you assess and describe it.

A scratched Hardlex crystal is not damage in the way a chipped sapphire is. It is a wear surface behaving as designed, and in many cases it can be polished out cheaply. So a watch that would be marked down for crystal damage if it were sapphire may be a straightforward refresh here.

But the opposite promise also applies. Do not tell a buyer the crystal is "scratch-resistant sapphire" because most modern watches are. Write Hardlex, which is what Seiko writes, and let the buyer price the difference themselves.

The magnifier is a separate part

The crystal is specified as Hardlex with magnified glass — a cyclops over the date, bonded on rather than formed in.

Bonded elements come off. It is rare, but it happens, and it usually starts as a faint ring or a slight lift at one edge before the whole thing detaches.

Look at it from several angles with light raking across the crystal. Check the date is centred and sharp under the lens rather than distorted at one side, which is a sign the magnifier has shifted.

This is exactly the kind of fault that does not appear in a seller's photographs, because a magnifier is almost always shot straight on and straight on is where it looks fine.

No accuracy figure is published — do not invent one

The Prospex and Presage pages on this site all publish a Precision line. This one does not, and neither does its 5 Sports stablemate.

The tempting move is to write "+25 to −15 seconds per day" because that is what Seiko quotes for its 6R calibres. Resist it. This is a 4R34, a different calibre, and the manufacturer has chosen not to state a figure for it.

The honest listing says what is published — automatic with manual winding, 24 jewels, approximately 41 hours — and, if the buyer asks about accuracy, reports what you measured on this example, described as your measurement.

Forty-one hours is also short enough to be worth flagging on its own. Off the wrist on Friday, stopped by Sunday.

A 24-hour bezel, not a dive bezel

Seiko lists the bezel as rotating with 24-hour display. It is not described as unidirectional.

That is correct for a GMT: the bezel indexes a time zone against the 24-hour hand, and there is no diving safety reason to restrict it. So a bezel that turns both ways here is behaving as specified, and a bezel that has been stiffened or that slips is the fault.

Set it against the 24-hour hand, let go, and confirm it holds.

The rest of the sheet

42.5 mm across, 13.6 mm thick, 46.0 mm lug to lug, 22 mm lug width, 161.0 g, rated 10 bar, magnetic resistance 4,800 A/m.

Worth noticing: 46.0 mm lug to lug on a 42.5 mm case. That is an unusually short span for the diameter, and it means this wears smaller than the number suggests — a genuinely useful thing to tell a buyer who is nervous about 42.5.

The case back is see-through and screwed, so look through it under a loupe at the 4R34 while the rotor turns.

LumiBrite is on the hands and indexes — not the bezel, unlike the Prospex divers here — so check those two against each other in the dark and do not expect the bezel to glow.