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Longines Hydroconquest 39mm Stainless Steel
Ref. L37804566
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Stepping up in the same colour and case shape
The HydroConquest line has always occupied a practical middle ground in Longines' catalogue — serious dive credentials without the dimensions of a dedicated tool watch. This 39mm version is the most balanced of the current range, and the 48.10mm lug-to-lug measurement is the reason: it follows the wrist's curve rather than bridging it, which keeps 166 grams of steel feeling settled rather than planted. The L888.5 inside is worth understanding. Longines starts from an ETA base and substantially reworks it, lowering the beat rate to 25,200 vibrations per hour for a smoother sweep and extending the power reserve to 72 hours. A silicon balance spring was added in later production, which removes the need to keep it away from magnets — a quiet but genuinely useful change for everyday wear. The ceramic bezel insert resists the surface scratching that aluminium accumulates over time, and the sapphire crystal is anti-reflectively coated on both faces, which is why the dial reads clearly at angles where most crystals wash out. The bracelet carries a diving extension in the clasp and micro-adjustment holes alongside it, so the fit can be dialled in precisely — the kind of detail that matters more on a sports bracelet worn close to the skin than it ever does on a dress watch.
- Reference
- L37804566
- Brand
- Longines
- Collection
- HydroConquest
- Case size
- 39mm
- Case thickness
- 12.20mm
- Lug width
- 19mm
- Case material
- Stainless steel
- Case shape
- Round
- Dial
- Black
- Crystal
- Sapphire
- Bezel
- Unidirectional rotating
- Movement
- Automatic
- Calibre
- ETA A31.L11
- Functions
- Date
- Water resistance
- 300m
- Bracelet / strap
- Stainless steel bracelet
- Strap colour
- Silver
- Clasp
- Folding clasp
- Lume
- Super-LumiNova
- Condition
- Pre-owned
- Retailer
- Mappin & Webb
Additional specifications
- Lug-to-lug
- 48.10mm
- Power reserve
- 72 hours
Learn more about Longines
Auguste Agassiz began trading watches in Saint-Imier in 1832, but the modern company dates from 1860, when his nephew Ernest Francillon built a factory in the meadows beside the Suze — the longines of the local dialect — and consolidated the scattered outworkers of the region under one roof.
Longines registered its winged hourglass in 1889. It is the oldest watch trademark still in continuous use.
The company's identity was built on precision and on timing things in public. It supplied chronographs for the first modern Olympic events it timed in 1896, timed the 1912 Federal Gymnastics Festival with a broken-wire mechanism accurate to a hundredth of a second, and developed the photo-finish camera and the quartz timing devices used across twentieth-century athletics.
Its aviation associations are equally deep. Longines instruments were carried by Charles Lindbergh across the Atlantic in 1927, and the Hour Angle watch, designed to Lindbergh's own specification to simplify longitude calculation, remains in the catalogue. Amelia Earhart and Howard Hughes both navigated by Longines.
The house was among the most decorated at nineteenth-century observatory trials, holding numerous precision records. Since joining the Swatch Group in 1983 it has occupied the accessible-heritage position: exclusive ETA-based movements, archive-driven designs through the Heritage line, and volume that makes it one of the group's most important brands.
- 1860
- Ernest Francillon builds the factory at Les Longines.
- 1889
- The winged hourglass is registered — the oldest watch trademark in use.
- 1912
- Broken-wire timing achieves hundredth-second accuracy.
- 1927
- Lindbergh crosses the Atlantic with Longines instruments.
- 1983
- Becomes part of the Swatch Group.
Also in 5 collections
This watch appears in Stainless Steel Watches (2,616), Automatic Watches (1,362), Sports Watches (675), Dive Watches (469) and Pre-Owned, Ex-Display & Vintage Watches (235).
What the specifications mean
A mechanical watch built to be worn hard and got wet.
Strengths
- 300m water resistance, rated for actual diving
- 39mm suits most wrists
- Sapphire crystal, which resists scratching
- 72-hour reserve survives a weekend off the wrist
- Luminous hands and markers for low light
Compare alternatives
Watches from other brands at a similar price, style and size, so you can see what else your budget can buy.
| Specification | L37804566 | R32145158 | 2731-ST-20001 |
|---|---|---|---|
| Price | £1,250 | £1,950 | £1,436 |
| Case size | 39mm | 43mm | 42mm |
| Water resistance | 300m | 300m | 100m |
| Movement | Automatic | Automatic | Automatic |
| Strap | Stainless steel bracelet | Stainless steel bracelet | Stainless steel bracelet |
| Power reserve | 72 hours | 59 hours | 38 hours |
| This watch |
|
|
Your new watch
Frequently asked questions, and things you should know about this watch
Can I swim with it?
Yes. At 300m it is rated for swimming, snorkelling and recreational diving.
Will the glass scratch?
Unlikely. Sapphire is second only to diamond in hardness and shrugs off everyday marking.
Does it need a battery?
No. It is automatic — the motion of your wrist winds it, and there is no cell to replace.
How long does it run for when it's not worn?
About 72 hours fully wound — enough to sit off the wrist over a weekend and still be running.
What size strap does it take?
19mm. Any strap of that width will fit, and on most modern watches quick-release bars make the swap a two-minute job with no tools.
Will it fit my wrist?
Lug-to-lug is 48.10mm, which suits wrists from roughly 16.5cm (6½ inches) upward.
Lug-to-lug decides fit more than case diameter does.
Is it a men's or women's watch?
Listed as unisex, and at this size it suits any wrist that takes the dimensions.
Cheapest place to buy
Mappin & Webb at £1,250, pre-owned. No UK retailer we track lists this reference new.
Is this available new?
Not from the UK retailers we track. This reference is listed as pre-owned only, at £1,250 from Mappin & Webb. A pre-owned watch has been worn, and is normally sold under the retailer’s own warranty rather than the manufacturer’s.
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