Seiko Astron GPS Solar Dual-Time Chronograph SSH175J1

Imagen: Seiko, web oficial

The storyWhy this reference matters

Astron is the word Seiko keeps for whatever arrives before anyone else. In 1969 it was the world's first quartz wristwatch; in 2012, the first mass-produced wristwatch that set itself from GPS signals and ran on light alone. The second feat was harder than it sounds: a GPS receiver draws a lot of power, and the whole point was feeding it from a solar cell hidden under the dial.

The 5X83 calibre appeared in 2024, the first GPS Solar Astron to combine a second time zone with a chronograph. That looks like simple addition and it is not. Motors and hands have to be shared out between local time, home time, the twentieth-of-a-second counter and the twelve-hour counter, without any one function eating the power reserve. Seiko introduced it as the highest-performing movement in the history of the line.

The SSH175J1 comes from the 2025 batch, which left the calibre alone and worked on the finishing instead. The titanium case gained mirror polishing on its flat surfaces, the bezel got a sapphire insert over titanium, and the subdial rings were diamond-cut. It arrived in May that year alongside the grey-dialled SSH177, the black-coated SSH179 and the SSH180, limited to 1,500 pieces.

SpecificationsThe numbers, in one table

IdentificationHow to tell it apart

A twentieth-of-a-second counter at twelve and a twelve-hour counter at six: that layout belongs to the 5X83 and will not be confused with a three-hand Astron. The SSH175 dial is greyish blue; the SSH177 is grey, the SSH179 goes all black with a hard coating, and the SSH180 mixes navy with rose-gold accents.

The bezel is titanium with a sapphire insert, and that detail places the watch in the 2025 generation: the first run of the 5X83, from 2024, used a two-piece bezel with ceramic. The measurements do not lie either — 44.1 mm across, 14.4 tall, 50 lug to lug.

Case and bracelet are titanium with a super-hard coating, and the whole thing weighs 110 grams, which is little for the size of it. The bracelet is integrated, meeting the case at fourteen millimetres. Double-domed sapphire with a super-clear treatment and 10 bar of water resistance.

CollectingWhat collectors check

This is a big watch and you need to try it on first: 44.1 mm with 50 lug to lug asks for a real wrist. Titanium makes up for the volume on the scales, not in the way it looks. Coming from a 40 mm automatic, the difference under a shirt cuff is obvious from day one.

Like every GPS solar it depends on two things, light and a clear sky. When buying, check the reserve indicator climbs in direct light and that manual signal reception completes its cycle next to a window. Running the chronograph daily eats far more power than leaving it stopped, so an example that has lived in a drawer may need a few hours of sun before it behaves normally.

The perpetual calendar runs to 2100 and the summer-time change is automatic, so the watch asks nothing of its owner beyond light. What does age is the rechargeable cell, replaceable at a service centre. Check the sapphire bezel insert: it barely scratches, but a chip in it is visible from the other side of the table.

Common questionsWhat people ask us about this reference

Keep readingWhere to go from here

Close relativesThe ones it gets confused with