The current Marathon 34mm General Purpose Mechanical (GPM) is a compact field watch with a Seiko NH35A automatic movement, tritium gas tubes, sapphire crystal and a high-impact composite case. Its stated dimensions and features make it straightforward to assess on paper, but the available evidence supports a specifications-led review—not a hands-on verdict about fit, timekeeping, brightness or durability.
Marathon GPM specifications at a glance
| Specification | Current black 34mm GPM listing |
|---|---|
| Case diameter | 34mm |
| Thickness | 12.5mm |
| Lug-to-lug | 41mm |
| Lug width | 16mm |
| Movement | Seiko NH35A, 24 jewels; automatic rotor winding and manual winding at the crown |
| Calendar | No calendar |
| Crystal | Sapphire |
| Illumination | Tritium gas tubes |
| Case material | High-impact composite Fibreshell |
| Water resistance | 3 ATM submersibility, as listed by Marathon |
| Manufacturer-stated standard | Marathon says the watch is manufactured in accordance with MIL-PRF-46374G, Type II, Class 4 |
These figures come from Marathon’s current US product listing. They describe the manufacturer’s stated specifications, not independent measurements or test results.
How the 34mm case may suit your wrist
The listed 34mm diameter and 41mm lug-to-lug provide concrete dimensions for comparing the GPM with watches you already own. Its 16mm lug width is relatively narrow compared with many contemporary watch straps, so strap choice and proportions are worth considering alongside the case size. Marathon lists the case as 12.5mm thick.
Those measurements cannot establish how the watch will look or feel on a particular wrist. If 34mm concerns you, compare the diameter and lug-to-lug measurement with a watch that fits you well, and check whether you like the narrower 16mm strap width. An anecdotal Reddit post uses the question “Worried about the 34mm case size?”; it is not evidence of a broader buyer consensus: r/Watches discussion.
#1 Best Overall
- Movement: ETA 2801
- No of Jewels: 17
- Scale Quantity: 2
- Scale Range: 1-12 (13-24)
- Luminous Features: Tritium Gas Tubes and MaraGlo
Movement: automatic and hand-windable
Marathon lists the Seiko NH35A, with 24 jewels and no calendar. The movement can receive power from its automatic rotor or be wound manually at the crown. That makes the current GPM an automatic watch with manual winding—not a manual-wind-only model.
Marathon’s current US listing does not state a power-reserve figure. A secondary dealer listing gives a different thickness figure of 11mm and mentions a typical 41-hour reserve; because those details are not confirmed by the current manufacturer listing, they should not be treated here as verified specifications. The secondary listing is available at Suvretta Corporation.
Rank #2
- COLLOQUIAL NAME: General Purpose Mechanical (GPM)
- MOVEMENT: NH35A
- SCALE QUANTITY [RANGE]: 2 [1-12 (13-24)]
- SUBMERSIBILITY: 3 ATM
- LUG WIDTH: 16mm
Tritium, sapphire and water resistance
Tritium gas tubes
The product page lists tritium gas tubes as the GPM’s illumination system. That establishes the stated technology, but not a particular brightness level, nighttime legibility result or lifespan. No independent test result is available here to support those claims.
Sapphire crystal
Marathon specifies a sapphire crystal. It is a useful material detail when comparing watches, but the listing alone does not establish how this particular watch will fare in real-world impacts or scratches.
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Rank #3
- MOVEMENT: High Torque quartz ETA FØ6 Movement
- CASE: Black Composite, 316L Stainless Steel case-back - CRYSTAL TYPE: Sapphire
- SUBMERSIBILITY: 3 ATM
- DIMENSIONS: 34mm Diameter / 12mm thickness
- LUG WIDTH: 16mm
3 ATM submersibility
The listed rating is 3 ATM. Marathon’s page does not provide a more detailed use recommendation in the evidence available here. Do not read the figure as a dive-watch rating or as proof of suitability for a particular water activity.
Military-spec language and the GPM’s history
Marathon identifies the black 34mm GPM as a “Field Mechanical, Type II” product and says it is manufactured in accordance with MIL-PRF-46374G, Type II, Class 4. That is Marathon’s product statement; it has not been independently verified here against the specification or through compliance testing.
Rank #4
- MOVEMENT: Sellita SW200-1 with Incabloc Shock Absorber
- NO OF JEWELS: 26
- CASE: 316L Stainless Steel
- LUMINOUS FEATURES: Tritium gas tubes and Maraglo
- DIMENSIONS: 41mm Diameter / 14mm thickness
Marathon also frames the General Purpose series as drawing on watches developed and issued to Allied forces in 1941, with lineage to the GG-W-113 specification of the 1960s. This is the manufacturer’s historical account, rather than an independently established history in this review. Both statements appear on the official product page.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Price, variants and warranty information
Prices vary by model and region, and can change. At the time reflected in the product listings gathered for this review, Marathon showed the black GPM at $575 USD on its US site, the desert-tan variant at $525 USD, and the black model at €550 on its Europe and UK listing.
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Best Value
- COLLOQUIAL NAME: General Purpose Mechanical (GPM)
- MOVEMENT: NH35A
- SCALE QUANTITY [RANGE]: 2 [1-12 (13-24)]
- CASE MATERIAL: High-Impact Composite Fibreshell
- LUG WIDTH: 16mm
| Listing | Displayed price snapshot | Warranty wording shown |
|---|---|---|
| Black 34mm GPM, US | $575 USD | Not stated in the cited US listing |
| Desert-tan 34mm GPM, US | $525 USD | Two-year international warranty, with an additional year available after registration |
| Black 34mm GPM, Europe and UK | €550 | Two-year warranty |
Check the listing for your specific market and variant before purchase; the warranty terms and displayed prices are not necessarily interchangeable. See Marathon’s desert-tan listing and Europe and UK listing.
Who should consider the Marathon GPM?
The GPM is worth considering if you want a compact field-style watch and value its particular combination of a 34mm case, automatic movement with hand-winding, tritium tubes, sapphire crystal and composite case. The listed measurements also make it possible to compare its fit-related dimensions with a watch you own before buying.
It is less straightforward to recommend if your decision depends on a proven water-use capability, independently tested illumination or timing performance, or a direct head-to-head ranking against another field watch. The available evidence does not establish those results or a dependable set of comparable competitor tests. Compare any alternative on the same points—dimensions, movement and winding, illumination, crystal, water-resistance rating, case material, strap width, market price and warranty—rather than relying on the field-watch label alone.
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Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon at the time of purchase will apply.
