The verdict, firstCyril Favre

Buy the 105 St Sa unless you actually cross time zones — then the UTC's 24-hour hand is worth the €300.

These two are the same watch until you reach the dial. Both are Series 105: a 41 mm bead-blasted steel case, 11.9 mm thick, roughly 47.3 mm lug-to-lug and 73 g without a strap, with a captive bidirectional bezel hardened by Sinn's TEGIMENT process under a black hard coating, sapphire front and screw-fastened display back, a screw-down crown, 200 m of water resistance to DIN 8310 and anti-magnetic protection to DIN 8309. Both arrived in November 2020. Neither is the more serious tool watch.

What separates them is the answer to one question: how do you want to read a second time zone? The 105 St Sa does it with the bezel — a 12-hour scale you rotate to an offset, plus an advancing minute scale for elapsed timing — and fills the dial with a day-and-date window. The 105 St Sa UTC gives you a dedicated orange 24-hour hand that jumps in one-hour steps, a 24-hour bezel, four more hours of power reserve, and no day of the week.

Sinn · ~$1,650105 St Sa

Sinn · ~$2,000105 St Sa UTC

The other case

The bezel trick on the 105 St Sa is real, but it is a trick you have to perform. You rotate, you read a 12-hour scale, and you still have to work out whether your second zone is in the morning or the evening. The UTC hand removes all of that: one glance, unambiguous, with AM and PM resolved by the 24-hour scale itself. It also brings the better movement architecture and a longer reserve, and its execution won a Red Dot Product Design Award in 2021. If you cross time zones more than a couple of times a year, the €300 is not a premium — it is the entire reason this version exists.

Where it is decided

4 arguments

Reading the second time zone

The 105 St Sa tracks a second zone on its bezel: rotate the 12-hour scale until the offset lines up, then read your second time against it. It works, and it costs nothing extra — but it is a 12-hour reading, and nothing on the watch tells you whether it is nine in the morning or nine at night where you are calling. The 105 St Sa UTC puts an orange arrow-tipped hand on a 24-hour track, so one glance gives you the hour and the half of the day together. It is a caller-style GMT: crown position 2 jumps the 24-hour hand in one-hour increments, and local time is set conventionally at position 3. With the 24-hour hand set to local time, you can also rotate the bezel to shift your reference zone while travelling without touching the crown at all. For anyone who coordinates across zones rather than merely visits them, this is not a close call.

Goes to

Sinn 105 St Sa UTC

Bezel, 12-hour basis
Orange jumping 24-h hand

What the bezel does when you are not travelling

This is where the cheaper watch wins, and it is not a consolation prize. The 105 St Sa's bezel carries two scales at once — a 12-hour scale for the second time zone and an advancing minute scale for elapsed time — with minute ratcheting and a luminous key mark. The same bezel therefore times a parking meter, a run or a pot on the stove, and tracks a second zone, on a case rated to 200 m. The UTC's bezel is a 24-hour scale with 24-hour ratcheting: excellent for adding a third zone on top of the 24-hour hand, and useless for timing anything shorter than a day. If your bezel gets used for minutes far more often than for time zones, the 105 St Sa is the more capable instrument of the two.

Goes to

Sinn 105 St Sa

12-h + minute scale, minute ratchet
24-h scale, 24-h ratchet

Movement and power reserve

Both movements are self-winding, run at 28,800 vph and hack. The 105 St Sa uses the Sellita SW220-1, the day-date sibling of the ETA 2836-2, with a 38-hour reserve. The UTC uses the Sellita SW330-1, built on the thinner 2892 architecture from which the ETA 2893-2 GMT derives, with 42 hours. Four hours is a modest margin rather than a transformative one, but it is a real one if you rotate watches and want yours still running after a weekend off the wrist. The more meaningful point is the base: the 2892-family architecture is the more refined platform, and it is what makes an independently jumping 24-hour hand possible at this price in the first place. Sinn publishes no accuracy specification for either watch and neither is chronometer-certified, so we make no claim there.

Goes to

Sinn 105 St Sa UTC

SW220-1, 38 h
SW330-1, 42 h

Calendar, dial clarity and what it costs

The 105 St Sa gives you the day of the week alongside the date, in English or German, at €1,550 on leather. The UTC gives you the date only, plus the 24-hour hand, at €1,850 on leather — roughly a €300 step on confirmed like-for-like configurations. Which way that reads depends entirely on what you need on the dial: a day window earns its space for most owners every single week, whereas a 24-hour hand earns its space only when there is a second zone worth tracking. The UTC's dial is also busier by one hand, which counts on a watch whose whole appeal is legibility. Otherwise the choice costs you nothing: both come in matt black with orange accents or matt white, both with luminous hands and indices, and both take the same 20 mm straps and bracelets.

Goes to

Sinn 105 St Sa

Day + date, €1,550
Date only, €1,850

Who should buy which

Sinn 105 St Sa

Your bezel gets used for minutes — a run, a parking meter, something on the stove — far more often than for time zones.
You want the day of the week on the dial and will actually read it.
You want the cleanest possible three-hand dial, with no extra hand crossing it.
You cross time zones rarely enough that a bezel offset handles it, and you would rather keep the €300.

See the 105 St Sa

Sinn 105 St Sa UTC

You coordinate with people in another time zone regularly and want the answer at a glance, not after a bezel rotation.
You want morning and evening resolved by the dial itself rather than inferred.
You want the 42-hour reserve and the 2892-architecture movement underneath it.
The orange 24-hour hand is the thing that makes the watch yours — it is the element that earned the UTC its 2021 Red Dot award.

See the 105 St Sa UTC

Your personal verdict

How often you genuinely need a second time zone, whether you use a bezel for minutes, and whether you read the day of the week can all flip this answer.

Find which 105 fits you

The rest of the Series 105

Each of the two watches compared above also comes with a matt white dial under a “W” reference, at the same price as its black-dial sibling. If the argument above settles the complication but not the dial, the answer is one of these four.

105 St Sa — day and date

105 St Sa UTC — 24-hour hand

Frequently asked

Do the Sinn 105 St Sa and 105 St Sa UTC share the same case?

Yes, identically. Both are 41 mm across, 11.9 mm thick, roughly 47.3 mm lug-to-lug and 73 g without a strap, in bead-blasted stainless steel, with 20 mm lugs, a captive bidirectional bezel in black hard coating on a TEGIMENT base, sapphire front with anti-reflective coating on both sides, a screw-fastened sapphire display back, a screw-down crown, 200 m of water resistance to DIN 8310 and anti-magnetic protection to DIN 8309. Nothing about the build separates them.

Is the Sinn 105 St Sa a real GMT watch?

Not in the mechanical sense. It has no independent hour hand and no 24-hour hand; it tracks a second zone by rotating the 12-hour scale on its bezel. That works, but it is a 12-hour reading you have to interpret. The UTC is the genuine GMT of the two — a caller-style one, where the 24-hour hand jumps in one-hour steps and local time is set conventionally.

Can the 105 St Sa UTC show three time zones?

Yes. Local time runs on the main hands, a second zone on the orange 24-hour hand, and a third by rotating the 24-hour bezel against that hand. The 105 St Sa cannot do this: its bezel is the only second-zone display it has, so rotating it is how you get your one extra zone rather than a third.

How much more does the 105 St Sa UTC cost?

About €300 on confirmed like-for-like configurations: €1,550 against €1,850 on leather at current EU retail including VAT. Both are up roughly 15 percent on their November 2020 launch prices, so figures quoted in launch-era reviews are out of date. Rubber, crocodile and steel bracelet options exist above those figures on both watches — confirm the exact configuration on sinn.de before comparing.

What is the trick where the UTC's 24-hour hand points north?

Sinn documents it in the UTC's instruction manual. Set the 24-hour hand to your local time, hold the dial horizontal and point the hour hand at the sun; the 24-hour hand then indicates north in the northern hemisphere, and south in the southern. During daylight saving time, advance the 24-hour hand by one hour first. The 105 St Sa has no equivalent, because it has no 24-hour hand.