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Bremont Supermarine 300M 40mm Mens Watch Green
Ref. SM40-ND-SS-GN-B
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Stepping up in Bremont's range
The current Supermarine represents a significant departure from what the line used to be. Bremont retired the distinctive multi-piece Trip-Tick construction and rebuilt the watch around a symmetrical 904L steel case — the same corrosion-resistant alloy common in serious diving equipment — with integrated crown and bezel guards that protect against accidental knock and adjustment without making the profile aggressive. At 12mm thick, it sits considerably flatter than its predecessors, and for a watch rated to 300 metres that is a meaningful choice: it will disappear under a shirt cuff in a way earlier Supermarines simply would not. The green gradient dial is the defining visual element, and Bremont has done something considered with it: the trapezoid bezel indexes continue inward across the dial as a naval crosshair, so the bezel and the dial read as a single composition rather than two separate components. The knurled unidirectional bezel carries a matching green anodised aluminium insert. In low or underwater light, the Super-LumiNova across the hands, indexes and bezel pip charges to a blue emission that contrasts cleanly against the green ground. The bracelet has been rebuilt alongside the case, and it shows. The push-button folding clasp incorporates micro-adjustment for fine-tuning fit through the day, and the quick-release mechanism allows strap changes without tools — practical on a dive watch, where swapping to rubber before getting in the water is routine. The BE-92AO inside draws its architecture from the Sellita SW300 but runs a Glucydur balance wheel, Anachron spring and Nivaflex mainspring, with a 50-hour reserve that covers a long weekend without winding.
- Reference
- SM40-ND-SS-GN-B
- Brand
- Bremont
- Collection
- Supermarine
- Case size
- 40mm
- Case thickness
- 12mm
- Lug width
- 20mm
- Case material
- Stainless steel
- Case shape
- Round
- Dial
- Green
- Crystal
- Sapphire
- Bezel
- Unidirectional rotating
- Movement
- Automatic
- Calibre
- BE-92AO
- Functions
- Date
- Water resistance
- 300m
- Bracelet / strap
- Stainless steel bracelet
- Strap colour
- Silver
- Clasp
- Folding clasp
- Lume
- Super-LumiNova
- Retailer
- Mappin & Webb
Additional specifications
- Lug-to-lug
- 49mm
- Power reserve
- 50 hours
Learn more about Bremont
Nick and Giles English founded Bremont in 2002, four years after their father died in a plane crash that Nick survived. All three had restored and flown vintage aircraft together, and the brand that emerged is inseparable from that. The name comes from Antoine Bremont, a French farmer who sheltered the brothers after an emergency landing.
Bremont set out to rebuild British watchmaking, which had effectively ended in the twentieth century. The early watches used Swiss movements in British-designed cases, with the Trip-Tick three-part case construction and a hardened outer barrel treated to over 2000 Vickers.
The military and aviation work is real rather than thematic. Bremont holds contracts with squadrons across the RAF, the US Air Force, and other services, producing issued watches for specific units, and has made watches for Martin-Baker ejection seat survivors — tested to the ejection forces themselves.
The company has also built watches incorporating material from historical objects: oak and copper from HMS Victory, aluminium from the Wright Flyer, and steel from Bletchley Park.
The manufacturing ambition advanced with the opening of a facility in Henley and the release of the ENG300 series in 2021, the first Bremont movement designed and largely made in England. Production is in the low tens of thousands annually.
- 2002
- Nick and Giles English found Bremont.
- 2007
- The first watches ship with the Trip-Tick case.
- 2009
- The Martin-Baker collaboration begins.
- 2021
- The ENG300 becomes the first English-made Bremont calibre.
Also in 7 collections
This watch appears in the Bremont Supermarine range (21), Stainless Steel Watches (3,546), Back in Stock (3,538), Automatic Watches (1,867), Sports Watches (860), Dive Watches (619) and Green Dial Watches (483).
What the specifications mean
A mechanical watch built to be worn hard and got wet.
Strengths
- 300m water resistance, rated for actual diving
- 40mm suits most wrists
- Sapphire crystal, which resists scratching
- Luminous hands and markers for low light
- Sits in the lower half of Bremont's range as we list it
Bremont Supermarine 300M alternatives
Watches from other brands at a similar price, style and size, so you can see what else your budget can buy.
| Specification | SM40-ND-SS-GN-B | 129372 | L37644966 |
|---|---|---|---|
| Price | £3,350 | £3,300 | £3,200 |
| Case size | 40mm | 41mm | 39mm |
| Water resistance | 300m | 300m | 300m |
| Movement | Automatic | Automatic | Automatic |
| Strap | Stainless steel bracelet | Rubber strap | Stainless steel bracelet |
| Power reserve | 50 hours | 38 hours | 72 hours |
| This watch | Closely matched | Closely matched |
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.
Water resistance explainedWill the glass scratch?
Unlikely. Sapphire is second only to diamond in hardness and shrugs off everyday marking.
Sapphire, mineral and acrylic comparedDoes it need a battery?
No. It is automatic — the motion of your wrist winds it, and there is no cell to replace.
Quartz, automatic and solar comparedHow long does it run for when it's not worn?
About 50 hours fully wound — enough to survive a night off the wrist, but not a full weekend.
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 49mm, which suits wrists from roughly 16.5cm (6½ inches) upward.
Lug-to-lug decides fit more than case diameter does.
How to size a watch to your wristIs it a men's or women's watch?
Listed as men's, though at 40mm it sits in the range that suits anyone.
Cheapest place to buy
Mappin & Webb is the only UK retailer we track stocking this reference, so there is nothing to compare it against today.
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