Tissot · Seastar 1000 and Supersport Chrono

Tissot T1204171104103 vs Tissot T1254171104100

10 published specifications differ between these two, and 3 are identical. Every figure below is what the manufacturer states for that reference; nothing is inferred from the other watch.

What differs

Specification	Tissot Seastar 1000 Chronograph 45.5mm, quartz, blue dialT1204171104103	Tissot Supersport Chrono 42mm, PVD-coated steel, blue dialT1254171104100
Case	316L stainless steel, 45.50 mm, with screw-down crown and caseback	316L stainless steel with PVD coating, 42.00 mm
Diameter	45.5 mm	42 mm
Thickness	12.82 mm	11.27 mm
Lug to lug	45.5 mm	42 mm
Water resistance	Water-resistant up to a pressure of 30 bar (300 m / 1000 ft) with screw-down crown and push-buttons	Water-resistant up to a pressure of 10 bar (100 m / 330 ft)
Crystal	Sapphire with double antireflective coating on top and bottom sides	Sapphire with one antireflective coating on bottom side
Bezel	Stainless steel with aluminium bezel ring, anti-clockwise rotating, with Super-LumiNova on the case	Stainless steel with an aluminium bezel ring
Bracelet	Stainless steel, reference T605046894, interchangeable quick release	Stainless steel, reference T605052437, interchangeable quick release
Clasp	Folding clasp with safety lock, diver extension and double push-buttons	Butterfly clasp with push-buttons
Movement notes	Battery voltage 1.55 volts. EOL battery end-of-life indicator, 30-minute and 1/10 second counters, central 60-second chronograph hand, ADD and SPLIT functions. Date. Total weight 180.00 g. Country of manufacture given as Switzerland, with a stated two-year warranty.	Battery voltage 1.55 volts. Battery end-of-life warning, thirty-minute and tenth-of-a-second counters, centre chronograph seconds hand, ADD and SPLIT. Date. Total weight 165.00 g. Country of manufacture given as Switzerland, with a stated two-year warranty.

What is identical

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

Lug width: 22 mm
Dial: Blue, with index markers and Super-LumiNova on the hands
Movement: Quartz chronograph PowerDrive

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.

Case back	Screw-down caseback	not stated
Crown	Screw-down	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 45.5 mm on the T1204171104103 against 42 mm on the T1254171104100 — a 3.5 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 T1204171104103, and put the figure in the listing rather than the diameter alone.

These reach different buyers

45.5 mm on the T1204171104103 against 42 mm on the T1254171104100. 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.

A visible difference in how they wear

1.6 mm of thickness separates these, with the T1204171104103 the taller at 12.8 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 T1204171104103 against 100 on the T1254171104100 — 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 T1204171104103's rating into the T1254171104100's listing.

What to check on each

T1204171104103

Unscrew both pushers before testing the chronograph. Tissot states the 30 bar rating with screw-down crown and push-buttons, so the pushers thread down and will not operate until released.
Grade the bezel ring as aluminium. It dulls, fades and takes dents rather than chipping, and a faded insert on this reference is honest wear rather than damage.
Exercise the ADD and SPLIT functions separately. Both are listed for this movement and a split that will not catch up to the running time is a fault a simple start-stop test misses.

T1254171104100

Examine the PVD coating at every edge and corner for breakthrough to the steel beneath. Coating wear is permanent, polishing removes more of it, and a bright patch on a dark case is the first thing a buyer sees.
Grade the aluminium bezel ring for fading and denting rather than for scratches, which is how aluminium wears.
Confirm the bracelet is the coated one and matches the case. A replacement steel bracelet against a PVD case is an obvious mismatch and a common bodge on coated watches.

Sources

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