Hand-winding is part of the Khaki Field Mechanical’s charm, and the Hamilton Khaki Field Mechanical Power Reserve 40mm adds the one thing many owners wish they had: a clear view of how much energy is left in the mainspring.

A power reserve indicator on the black dial runs from F for full to E for empty, giving the design a purposeful, instrument-like feel that suits its military lineage. Behind it is the H-23, a manual-winding caliber developed by ETA exclusively for Hamilton, storing up to 80 hours of power and fitted with a Nivachron balance spring. Hamilton presents it as honoring the heritage design and essential functionality of the Khaki family while adding a genuinely useful modern complication.

The 40mm steel case is 11.95mm thick and 48mm lug to lug, a balanced size for most wrists. Sapphire with anti-reflective coating keeps the dial easy to read, and 100m of water resistance is a step up from the classic Khaki Field Mechanical. A khaki green NATO-style strap seals the field-watch look.

Hamilton Khaki Field Power Reserve 40mm, Ref. H69509930

• Reference: H69509930
• Case: 40mm stainless steel, 11.95mm thick, 48mm lug to lug
• Dial: black with F-to-E power reserve display
• Movement: H-23 manual winding, developed by ETA for Hamilton
• Power reserve: 80 hours, shown on the dial
• Nivachron balance spring; Super-LumiNova
• Crystal: sapphire, anti-reflective coating
• Water resistance: 10 bar (100m)
• Strap: khaki green textile NATO-style, 20mm pin buckle

Wind it until the hand reads F, and enjoy a field watch that tells you exactly when it needs you.