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The GMT complication has a size problem.

Most watches with a second time zone function run 41mm, 42mm, or larger. The reasoning is partly practical — a rotating bezel needs real estate — and partly cultural, because the watches that defined the category in the public imagination, the Rolex GMT-Master on the wrist of a Pan Am pilot, the Submariner's bigger sibling — all wore large by modern standards and large by the standards of their own era.

The assumption that GMT watches need to be big is wrong. The five references on this list prove it. Each one delivers a genuine GMT complication in a case at 40mm or under, each one does something the others cannot, and each one is worth owning on its own merits.

The name comes from a Longines dual time zone wristwatch produced in 1925, which featured the Zulu flag on the dial. Zulu time is the universal aviation time standard — identical to Greenwich Mean Time — and Longines has been building watches around it for a century. That history matters because the Spirit Zulu Time is not a homage to anything. It is a continuation.

The 39mm case arrived in 2023, a direct response to the original 42mm version's tendency to overwhelm smaller wrists. The reduction was not cosmetic. Longines reduced the lug-to-lug to 46.8mm, kept the ceramic 24-hour bezel and the COSC-certified movement, and delivered the same genuine GMT function in a package that actually fits. The L844.4 caliber beats at 25,200 vibrations per hour with a monocrystalline silicon balance spring and 72 hours of power reserve.

The case thickness of 13.5mm is the only criticism worth making. For a 39mm watch, it wears tall. Buyers who have tried the original should know that going in. Everyone else will find a watch that is confident about what it is — a tool, a pilot's instrument, a serious GMT at an honest price point — without needing a larger canvas to say so.

Specs:

The Superman has been YEMA's flagship dive watch since 1963. It equipped French Navy divers, French Everest expedition climbers, and eventually became a cult reference for collectors who found it before the brand's recent resurgence. The Worldtime GMT is what happens when YEMA takes that heritage seriously rather than just trading on it.

The case is 39mm in diameter, 13.7mm thick, and 48mm lug-to-lug. Fully brushed 316L stainless steel with pointed lugs that read immediately as vintage without reproducing any specific historical reference. The double-domed sapphire crystal adds distortion at the edges that reinforces the retro character. The shovel-shaped seconds hand with its red pip is lifted directly from the 1970s Superman models and is the clearest signal that Yema understands what makes this watch interesting.

The movement is the in-house YEMA3000 GMT caliber, designed and assembled in Morteau, France. This is the same movement in the Navygraf Marine Nationale GMT and it earns its place here just as it does there — an independently produced GMT caliber from a brand at this price point is genuinely unusual. The 24-hour graduated bezel tracks a second time zone against the GMT hand, and the combination of hand, bezel, and local hour hand allows three simultaneous time zones.

The Paris dial variant adds a green sunburst dial that reads differently in different light. It is the version most likely to hold your attention after the specs stop mattering.

YEMA is the most interesting watch brand most serious collectors are not paying enough attention to. The Superman Worldtime GMT is the clearest evidence of why that will not remain true indefinitely.

Specs:

(If you are circling one of these references and want help deciding which one fits your wrist, your budget, and how you actually live — that is exactly what the Watch Consult is for. Thirty minutes, $97, no brand affiliations. Book at tidycal.com/ianmatthewroth/watchconsult.)

The IWC Pilot's Watch UTC was introduced in 1998 and ran in various forms until the mid-2000s. It was never the loudest watch in the IWC lineup, which is partly why the pre-owned market has not fully caught up to what it is.

The 39mm steel case is based on the same architecture as the Mark XV — the pilot's watch IWC was producing concurrently — with a slightly larger diameter to accommodate the second time zone display. That display is a 24-hour disc that rotates once per day under an arched window at 12 o'clock, showing UTC. The local hour hand is independently adjustable, which means crossing a time zone requires only a push and rotation of the crown to move the local hand forward or back in one-hour increments without disrupting the running seconds or the UTC display.

The movement is the IWC Caliber 37526, based on the ETA 2893-2, with an anti-magnetic soft-iron inner case — a pilot's watch requirement that IWC has never abandoned. The black dial, applied Arabic numerals, and large Superluminova-coated hands make it one of the most legible watches on this list in any light condition.

Pre-owned examples in good condition with original strap or bracelet range from $3,200 to $4,800 depending on reference and condition. The Spitfire variants command a slight premium. All of them are undervalued relative to what they deliver.

Specs:

The 16710 ran from 1989 to 2007 and is the last GMT-Master II produced with an aluminum bezel insert. That is simultaneously its greatest vulnerability and its defining character. The aluminum Pepsi bezel — red and blue anodized, prone to fading and scratching, impossible to replicate exactly — is the thing that makes every 16710 Pepsi unique. Two examples from the same year will look different after thirty years of wear. One will be vivid; one will have faded toward something softer. Neither is wrong.

The 40mm Oyster case runs the Caliber 3185 in early production and the 3186 in later references from around 2007. Both are Rolex-certified chronometers with the Parachrom hairspring introduced in the 3186. The bracelet received the solid end link upgrade mid-production, making post-1999 examples easier to wear without the hollow end links that plagued earlier references.

The movement allows the local hour hand to be set independently of the GMT hand, which means the 16710 functions as a true two-timezone watch. The bidirectional bezel tracks a third. Three time zones from a watch produced before most of the people reading this had a smartphone.

Pre-owned pricing has held firm. Clean examples with papers and box run $14,000 and up through infinity. Honest examples without papers or with faded bezels can be found for less. The faded bezel is not a defect. It is a record.

Specs:

Marcus Hale, the protagonist of my debut novel The Cave: What the Earth Keeps, wears an Explorer II 16570. White dial. He keeps the GMT hand pointed at Jerusalem time — three hours ahead of wherever he is. He does not change it. The watch belonged to someone he lost in Iceland. He put it in a box for three years after she died. When he finally opens the box and winds the crown again at the end of Chapter 1, it is one of the clearest signals in the book that something has shifted.

I gave Marcus my watch because I understand the 16570 the way I understand very few things. I have been writing about this reference for two years across fourteen articles, and I will not pretend there is a more important watch on this list — not for me, and probably not for most people reading OTW.

Here is what the specs say: 40mm Oystersteel case, Caliber 3185 in early production and 3186 in later references, fixed 24-hour graduated bezel, independent GMT hand, sapphire crystal, 100 meters of water resistance. Produced from 1989 to 2011. White dial or black. The white — called Polar — is the one most collectors reach for, the one that photographs best, the one that looks exactly like nothing else at any price.

Here is what the specs do not say: the 16570 is the last Explorer II at 40mm. Every reference that followed grew to 42mm. The proportions that made this watch — the fixed bezel, the slim case, the GMT hand visible but not loud against the white dial — belong to a production run that ended fifteen years ago and will not return.

Pre-owned pricing ranges from $6,000 on honest examples without papers to $10,000 on pristine full sets. The white dial commands a slight premium. Both are correct.

The Cave: What the Earth Keeps publishes in 2026. If the watch on Marcus's wrist made you want to read Chapter 1, you can find the ROUGH draft here.

Specs:

The sub-40mm GMT market is thin for a reason. The complication demands precision engineering that most manufacturers build into larger cases because larger cases are easier to work with. The five references on this list found different ways around that constraint — Longines with movement miniaturization, Yema with an in-house caliber built from scratch, IWC with a disc display that sidesteps the rotating bezel problem entirely, Rolex twice over with the kind of execution that does not need to justify itself.

The best GMT watch is the one that fits your wrist and does not make you think about the fact that it is tracking two time zones. All five of these qualify.