CWC — the Cabot Watch Company — is the least famous watch brand most serious military watch collectors know by name. Founded in Huddersfield in 1972 by Ray Mellor, a former UK Managing Director of Hamilton, CWC was established specifically to maintain British Ministry of Defence contracts after Hamilton ceased UK operations. The company is named after John Cabot, the Bristol-based explorer who sailed from England in 1497 — a deliberate nod to the brand's British heritage and its founder's belief that British precision had something to add to the world.

CWC's credentials are not borrowed from history. They are ongoing. CWC has been the official supplier of quartz field watches to the British Armed Forces since 1980, when the G10 replaced the earlier W10. CWC has supplied dive watches to the Royal Navy and special forces units including the Special Boat Service since the early 1980s, when rising Rolex Milsub prices led the MoD to approach CWC for a replacement. Today, CWC produces watches under active MoD contract — these are watches worn in current operational service, not nostalgic reproductions.

The strap story for CWC watches is also a British military story. The grey nylon strap issued with CWC watches is made to DefStan 66-15 — the British Defence Standard for wristwatch straps — and is supplied to the MoD in thousands of units per year. CNS's single-pass nylon range is built to the same specification.

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CWC Strap Sizes and Spring Bar Types — Critical Information

The CWC range uses two different strap systems, and getting this right is more important for CWC than for almost any other watch.

CWC G10 Quartz (all generations — standard, Fatboy-80, GS Sapphire) — fixed welded spring bars. The G10's spring bars are welded to the case as part of its MoD specification, preventing accidental spring bar release during military operations. This means standard two-piece straps cannot be fitted using conventional spring bar tools. The correct strap choice is a single-pass through-strap that threads between the case and the fixed bars.

CWC's own specifications confirm: 18.5mm lug width on the standard G10 and GS Sapphire, 19mm on the G10 Fatboy-80 reissue. An 18mm single-pass nylon strap fits the standard G10 correctly. A 20mm single-pass will fit with some tension.

CWC Royal Navy Diver Quartz (RN300 QS120, Mk.2 and all diver variants) — standard removable spring bars. CWC confirms: 20mm lug width, 41mm case (excluding crown), 47mm lug-to-lug. The full CNS range at 20mm fits directly.

CWC Royal Navy Diver Automatic (mechanical variants) — standard removable spring bars, 20mm lug width. Same case as the quartz diver.

CWC SBS (Special Boat Service) issue watch — 20mm standard spring bars. CWC's own issued strap for the SBS is their 20mm military nylon.

Quick reference:

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Best Straps for the CWC G10 — Single-Pass Only

Because the G10's spring bars are welded, only single-pass through-straps and open-ended straps work. CNS single-pass nylon threads through the fixed bars correctly.

Single-pass nylon — Original at 18mm — the most factory-correct and most operationally coherent G10 strap. CWC issues the G10 on a grey DefStan-spec nylon strap as standard. The CNS single-pass nylon is built to the same DefStan 66-15 specification in the same ballistic nylon construction. The most appropriate G10 colourways:

• Admiralty Grey — the exact colourway of the factory-issued CWC strap. The most historically correct G10 combination — the grey that MoD procurement selects.
• Black — the most operational alternative. Suits all G10 dial variants.
• Olive / khaki — for a more field-adjacent character, referencing Army issue equipment rather than the Naval grey.
• Black and grey — the most collector-appropriate combination.

RAF single-pass nylon at 18mm — the RAF 6B/2617 specification strap. The RAF strap and the G10 emerge from the same British military procurement world — both were developed under MoD specification in the same era, for the same British Armed Forces. The RAF strap on the G10 creates the most specifically British military heritage combination available.

Important fitting note for the G10: The spring bars on the G10 are fixed — the single-pass strap threads between the spring bar and the case back on one side, and between the spring bar and the lug on the other. This is the standard single-pass fitting method and requires no tools. The strap does not need to be removed to change — loosen the buckle, slide the strap through the bars.

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Best Straps for the CWC Royal Navy Diver (20mm)

The Royal Navy Diver's standard removable spring bars and 20mm lug width give the full CNS range direct access.

Single-pass nylon — Original at 20mm — the most factory-correct combination. CWC issues the diver and SBS watches on their 20mm grey military nylon as standard. The CNS DefStan 66-15 single-pass at 20mm is the direct equivalent in CNS construction. Most appropriate colourways:

• Admiralty Grey — the factory-issued CWC colourway for the diver and SBS. The most operationally correct Royal Navy Diver combination.
• Black — for the most minimal operational combination.
• Olive / khaki — for a broader military character.
• Navy — particularly appropriate for a Royal Navy-issued dive watch.

RAF single-pass nylon at 20mm — the most specifically British military heritage nylon for the diver. The RAF strap's 1954 British service heritage connects directly to the Royal Navy operational world.

Marine Nationale elastic at 20mm — the most comfortable Royal Navy Diver daily wear option. The French Navy combat swimmer heritage of the Marine Nationale strap connects directly to the professional military diving world the CWC diver was designed for — the same post-war era of Western naval special operations. Available in navy and black.

Canvas at 20mm in olive or black — for the most specifically military field-equipment character.

Classic FKM rubber in black at 20mm — the most practical waterproof choice for the diver's 300m water resistance.

Brown vintage two-stitch calfskin at 20mm — for the Royal Navy Diver in dress-sport contexts. CWC's own premium leather strap is offered specifically for diver owners who want a smart combination. The warm brown creates a temperature contrast against the dark case and dial.

Classic black calfskin at 20mm — the most formal diver combination for smart-casual and business contexts.

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The DefStan Heritage — Why CNS Nylon Is Specifically Appropriate

CWC's own issued straps are built to DefStan 66-15 — the British Ministry of Defence standard for wristwatch straps. CNS's single-pass nylon range is also built to DefStan 66-15 specification: ballistic nylon webbing, welded (not stitched) construction to prevent fraying, and matte hardware that does not reflect light.

This is not incidental. CNS's British military strap heritage means that fitting a CNS single-pass nylon to a CWC G10 or Royal Navy Diver is not merely an aftermarket upgrade — it is replacing a MoD-spec strap with another MoD-spec strap from a different manufacturer. Both the watch and the strap come from the same British military procurement standard.

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Recommended Combinations

G10 — most historically correct — Admiralty Grey single-pass nylon at 18mm — the factory-issued colourway on a DefStan 66-15 spec strap.

G10 — most specifically British military heritage — RAF single-pass nylon at 18mm — RAF 6B/2617 specification meets the G10's own MoD specification.

Royal Navy Diver — most operationally correct — Admiralty Grey single-pass nylon at 20mm — the CWC factory-issued colourway.

Royal Navy Diver — most specifically naval — navy single-pass nylon at 20mm — Royal Navy blue on a Royal Navy watch.

Royal Navy Diver — most comfortable active — Marine Nationale elastic at 20mm — naval combat swimmer heritage.

Royal Navy Diver — most characterful off-duty — brown vintage two-stitch leather at 20mm — the operational dive watch becomes a dress-sport piece.

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Frequently Asked Questions

What size strap does the CWC G10 take? The CWC G10 standard and GS Sapphire use 18.5mm fixed welded spring bars. The G10 Fatboy-80 reissue uses 19mm fixed welded spring bars. Because the spring bars are welded, only single-pass through-straps are compatible — standard two-piece straps cannot be fitted. CNS single-pass nylon at 18mm threads through the fixed bars correctly.

What size strap does the CWC Royal Navy Diver take? 20mm — confirmed by CWC's own official specifications. The diver uses standard removable spring bars, so the full CNS range at 20mm fits directly.

Why does the CWC G10 have fixed spring bars? The G10's spring bars are welded to the case as part of its MoD specification — a deliberate design choice to prevent accidental spring bar release during military operations. Losing a spring bar in the field means losing the watch. Welded spring bars eliminate this failure mode at the cost of strap-changing flexibility.

What is the DefStan 66-15 specification? DefStan 66-15 is the British Ministry of Defence standard for wristwatch straps — specifying material construction, width tolerances, hole spacing, hardware finish, and durability requirements. CWC's issued grey nylon strap meets this standard. CNS's single-pass nylon is built to the same specification, using ballistic nylon webbing and welded (not stitched) construction as the standard requires.

What is the difference between the G10 and the Royal Navy Diver? The G10 is a general service field watch — 36-38mm, quartz, 10mm thick, designed for land operations and general military issue. The Royal Navy Diver is a professional dive watch — 41mm (excluding crown), 300m water resistance, designed for Royal Navy and special forces underwater operations. Both are current CWC production watches under active MoD contract.

CNS single-pass nylon for the CWC G10 is available at 18mm. CNS straps for the CWC Royal Navy Diver are available at 20mm. Standard delivery worldwide. 30-day returns.