This watch is model 100AT/24/SS/SL/22. Below you will find a full description of this specific watch, together with the issue it has (or is reported to have). In many cases, these watches turn out to have no significant problem at all. Following that is the complete factory specification, including dimensions, features, and technical details.

We acquire these watches through defence auctions, military surplus clearances, and other official disposal sales. It is quite common for watches sold through these channels to be listed as faulty or unserviceable when, in reality, there is little or nothing wrong with them. Where faults do exist, they are usually minor and straightforward to rectify.

These items are often disposed of at low cost simply because service departments, both in the UK and elsewhere, are working under time constraints and may only have had the opportunity to carry out a brief inspection. If nothing obvious is found, the watch may still be marked for disposal rather than undergoing further testing. In practice, this usually means one of three things: there is no real fault, a minor issue may reveal itself over time, or the watch may require only a routine service, repair, or battery change depending on the model.

Model

100AT/24/SS/SL/22

Condition

Excellent, as shown in the photographs.

Reported Fault

Running well, but the second hand requires resetting. This would be a routine and inexpensive job for any competent watchmaker.

FACTORY DESCRIPTION

SKU

100AT/24/SS/SL/22

The MWC Depthmaster range of military divers’ watches is MWC’s latest heavy-duty series. These watches are exceptionally robust, fitted with a sapphire crystal, and designed for professional diving with mixed gases at extreme depths thanks to their 100ATM / 1000m water resistance rating.

They also feature a wider 24mm strap (most military divers’ watches use 20mm straps) and a scratch-resistant ceramic bezel, which offers improved grip in cold or icy conditions. This model is equipped with GTLS tritium tubes for outstanding night-time and low-light visibility.

The Depthmaster range has been specifically developed for professional divers operating in harsh and demanding environments.

Helium Escape Valve

All MWC 100ATM models are fitted with a helium escape valve.

Many people ask how helium can enter a watch case if the seals are functioning correctly. The answer is simple: helium molecules are among the smallest known gas molecules, small enough to pass through seals that remain fully watertight against water and larger gases.

This is particularly relevant for saturation divers, who spend extended periods in high-pressure environments breathing helium-rich gas mixtures. Over time, helium can build up inside the watch case. During decompression, this trapped pressure can potentially damage the watch or even force out the crystal or crown when unscrewed.

The helium valve solves this by automatically allowing helium to escape during decompression while preventing anything external from entering the case.

Although most recreational divers will never need such a feature, it is essential on a true professional deep-diving watch. Without it, the watch would not be fully fit for purpose in saturation diving conditions.

Movement

High-quality Swiss Ronda 715Li Quartz movement with:

• 10-year battery life
• Hacking function for precise synchronisation

Dimensions & Specification

• Movement: Swiss Ronda 715Li Quartz
• Battery Life: 10 Years
• Water Resistance: 100ATM / 1000M / 3,280ft
• Crown: Screw-down
• Helium Escape Valve: Yes
• Case Width: 47mm including crown / 44mm excluding crown
• Bezel: Unidirectional, non-reflective, ceramic insert
• Thickness: 18mm
• Crystal Diameter: 31mm
• Crystal: Sapphire with anti-reflective coating
• Lug to Lug: 48mm
• Weight: 140g
• Case Material: 316L Stainless Steel
• Illumination: GTLS Tritium on hands and markers, Luminova on bezel
• Strap: 24mm NATO webbing strap

Why Sapphire Crystal?

Many customers ask about the advantages of sapphire crystal over standard mineral glass.

Synthetic sapphire is widely regarded as the best material for watch crystals because it is:

• Highly scratch-resistant
• Extremely strong
• More shatter-resistant than mineral glass
• Ideal for demanding environments

These qualities make it especially popular with military personnel, police officers, security professionals, and outdoor users.

In our experience, the vast majority of cracked watch crystals we see are mineral glass rather than sapphire. Even hardened mineral glass does not approach sapphire’s durability under harsh conditions.

Sapphire crystals are heat-treated during manufacture to remove internal stresses, improving strength further, and are then finished with anti-reflective coatings for excellent clarity.

It is a premium material, which is why it is generally reserved for higher-end watches.