Hamilton
Khaki Field Mechanical 38mm
H69439931 · 38mm · 50m
WWII MIL-W-3818 silhouette, hand-wound.
Two field watches that are actually spec-correct
Most 'field watches' are aesthetic homages. Both of these are different. Hamilton's Khaki Field Mechanical is a deliberate reissue of the MIL-W-3818 specification (38mm, 24-hour inner track, hand-wound) that Hamilton issued to US Army personnel from 1942 onward. Marathon GPM is the watch the Canadian Armed Forces still currently issues to non-pilot personnel, with NSN cataloguing and tritium-tube illumination.
Spec sheet
| Attribute | Hamilton Khaki Field Mechanical 38mm | Marathon GPM (General Purpose Mechanical) |
|---|---|---|
| Reference | H69439931 | WW194004BR |
| Case diameter | 38mm × 9.5mm | 41mm × 13mm |
| Water resistance | 50m | 60m (3-bar military spec) |
| Movement | ETA 2801-2 hand-wound | Sellita SW200-1 automatic |
| Reserve | 80 hours | 38 hours |
| Crystal | Sapphire | Sapphire (anti-reflective) |
| Illumination | Super-LumiNova C3 | Tritium tubes (H3, 25-year half-life) |
| Spec | MIL-W-3818 reissue (cosmetic) | Currently issued, NSN catalogued |
| Retail | ~€500 | ~€700 |
Heritage vs current-issue
Hamilton Khaki Field Mechanical is a heritage product: 1942 design, modern manufacture, sold to civilians. The hand-wound 80-hour H50 movement (an ETA 2801-2 with extended balance/spring) is genuinely well-engineered for the price.
Marathon GPM is current-issue. The Canadian Armed Forces orders these directly from Marathon for non-pilot field personnel. NSN (NATO Stock Number) cataloguing means each piece is qualified to mil-spec procurement. Tritium tubes provide always-on illumination without needing 'charging'.
Tritium vs Super-LumiNova
Super-LumiNova on the Hamilton needs charging from a light source, then glows for ~6-8 hours decreasingly. Tritium tubes on the Marathon are sealed self-luminous (gas-filled vials with phosphor coating) and produce constant illumination day-and-night for ~25 years before falling below useful brightness. For genuine night-use this is a meaningful difference.
Build feel
Hamilton at 38mm × 9.5mm is the truer-to-spec sizing and reads like a 1940s field watch. Marathon at 41mm × 13mm is closer to a modern dive-watch silhouette but built to mil-spec impact tolerances (the bezel is rotating but unidirectional and has a captive, replaceable construction).
Pros and cons
Khaki Field Mechanical 38mm · Pros
- 80-hour reserve (H50 movement)
- True-to-period 38mm sizing
- €500 entry tier
- Hand-wound (ritual / minimalist)
Khaki Field Mechanical 38mm · Cons
- Cosmetic mil-spec only (not actually issued)
- Super-LumiNova fades during night
- 50m WR is dress-spec
GPM (General Purpose Mechanical) · Pros
- Currently mil-issued, NSN catalogued
- Tritium tubes (constant night illumination)
- Sellita SW200 automatic
- 60m mil-spec WR
GPM (General Purpose Mechanical) · Cons
- More expensive at €700
- Modern 41mm sizing (less period-accurate)
- Sellita is a workhorse but unspectacular movement
Verdict: which one?
If you want a spec-accurate WWII-style field watch: Khaki Field Mechanical 38. €500, 80-hour H50 movement, 38mm.
If you want a genuinely current-issue military watch with constant night illumination: Marathon GPM. €700, tritium-tube illumination, NSN-catalogued.
Both work as one-watch pieces for an outdoor / utility-leaning rotation. Marathon gets the edge if night-readability matters; Hamilton wins on classical proportions.
Common questions
What's the difference between the Hamilton Khaki Field Mechanical 38mm and the Marathon GPM (General Purpose Mechanical)?
Two affordable field watches with mil-spec credentials. Hamilton Khaki Field Mechanical at the WWII MIL-W-3818 silhouette against the Marathon GPM, an actually-issued Canadian-military reference.
Hamilton Khaki Field Mechanical 38mm or Marathon GPM (General Purpose Mechanical): which should you buy?
If you want a spec-accurate WWII-style field watch: Khaki Field Mechanical 38. €500, 80-hour H50 movement, 38mm.
When were the Khaki Field Mechanical 38mm and GPM (General Purpose Mechanical) introduced?
The Hamilton Khaki Field Mechanical 38mm was introduced in WWII heritage / 2017 reissue; the Marathon GPM (General Purpose Mechanical) in Currently issued.
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