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Doxa Sub 300T Aquamarine 42.5mm Mens Watch
Ref. 840.10.241.10
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Stepping up in Doxa's range
The original Conquistador of 1969 was a milestone in dive watch history — the first watch sold to the general public with a helium escape valve built in. This is the 2019 tribute to that watch, and it earns the connection rather than just claiming it: the cushion case is drawn directly from the original, the helium valve sits where it always did, and the bezel carries Doxa's patented dual-scale system that reads both depth in feet and elapsed minutes for calculating no-decompression limits, something no other brand offers in quite this form. What makes the proportions unusual is the lug-to-lug distance of 44.5mm on a case that is 42.5mm across. That near-square footprint means the watch sits far closer to the wrist than the diameter alone would suggest, and at 13.65mm thick it is not a slim watch, but it carries that mass low. The Beads of Rice bracelet is screwed directly into the case rather than pinned, and the folding clasp includes a ratcheting extension for a wetsuit — details that point to a watch designed around actual diving rather than the appearance of it. The Sellita SW200-1 inside is a straightforward choice, and a correct one: it is robustly built, easy to service anywhere in the world, and appropriate for a tool watch that may actually go to depth.
- Reference
- 840.10.241.10
- Brand
- Doxa
- Collection
- SUB 300T
- Case size
- 42.5mm
- Case thickness
- 13.65mm
- Lug width
- 20mm
- Case material
- Stainless steel
- Case shape
- Round
- Dial
- Blue
- Crystal
- Sapphire
- Bezel
- Unidirectional rotating
- Movement
- Automatic
- Calibre
- Sellita SW200-1
- Functions
- Date
- Water resistance
- 1200m
- Bracelet / strap
- Stainless steel bracelet
- Strap colour
- Silver
- Clasp
- Folding clasp
- Lume
- Luminous
- Retailer
- Mappin & Webb
Additional specifications
- Lug-to-lug
- 44.5mm
- Power reserve
- 38 hours
- Origin
- Swiss made
Learn more about Doxa
Doxa was founded by Georges Ducommun in Le Locle in 1889, and spent its early decades on pocket watches and, notably, dashboard clocks for the emerging car industry — supplying Bugatti among others.
Its lasting contribution came much later. In 1967 Doxa released the SUB 300, developed in consultation with professional divers, and it introduced several things now taken for granted. The dial was orange, chosen after testing which colour remained visible longest as depth filtered out light. The bezel carried a US Navy no-decompression scale rather than simple minute markers, letting a diver read safe bottom time directly. The beads-of-rice bracelet included an expansion section to fit over a wetsuit.
Jacques Cousteau's organisation distributed the watches, and US Divers sold them in America. The SUB became genuine professional equipment rather than a dive-styled dress watch, and it appears throughout Clive Cussler's novels on the wrist of Dirk Pitt.
Doxa struggled through the quartz era and was largely dormant before being revived by the Jenny family, who reissued the SUB faithfully from 2002 onward.
The modern range remains almost entirely dive watches, with the same cushion case, the same bezel scale, and dial colours named for their depth-rating heritage — Professional orange, Sharkhunter black, Searambler silver, Caribbean blue.
- 1889
- Georges Ducommun founds Doxa in Le Locle.
- 1908
- Supplies dashboard clocks to early car manufacturers.
- 1967
- The SUB 300 debuts with an orange dial and decompression bezel.
- 2002
- The SUB is reissued under new ownership.
Also in 6 collections
This watch appears in Stainless Steel Watches (3,308), Back in Stock (2,703), Automatic Watches (1,651), Blue Dial Watches (902), Sports Watches (816) and Dive Watches (578).
What the specifications mean
A mechanical watch built to be worn hard and got wet.
Strengths
- 1200m water resistance, rated for actual diving
- 44.5mm lug-to-lug keeps the 42.5mm case wearable
- Sapphire crystal, which resists scratching
- Luminous hands and markers for low light
Worth knowing
- 38-hour reserve means winding it after a day off
Doxa Sub 300T Aquamarine alternatives
Watches from other brands at a similar price, style and size, so you can see what else your budget can buy.
| Specification | 840.10.241.10 | 182800000016 | FC-301N3B6 |
|---|---|---|---|
| Price | £1,890 | £2,400 | £1,795 |
| Case size | 42.5mm | 42mm | 38.5mm |
| Water resistance | 1200m | — | — |
| Movement | Automatic | Automatic | Automatic |
| Strap | Stainless steel bracelet | — | Leather strap |
| Power reserve | 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 1200m 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 38 hours fully wound — so it will usually stop if you leave it off overnight.
What size strap does it take?
20mm. 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 44.5mm, which suits wrists from roughly 16cm (6¼ inches) upward.
Lug-to-lug decides fit more than case diameter does.
Is it a men's or women's watch?
Listed as men's.
Cheapest place to buy
Mappin & Webb is the only UK retailer we track stocking this reference new, at £1,890. There is nothing to compare it against today.
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