Hamilton H76409530 Khaki Aviation Pilot Pioneer Mechanical Chrono 40mmWith a distinct vintage military aviation design, the Khaki Pilot Pioneer Mechanical Chronograph brings back the form and function of the chronographs issued to British Royal Air Force pilots in the 1970s. Rugged and reliable, the 40mm watch is powered by our exclusive hand-wound H-51-Si movement.KHAKI AVIATIONThe Khaki Aviation collection perfectly displays Hamilton's technical know-how when it comes to creating reliable watches for pilots and urban aviators. FEATURES MANUAL WINDINGWind your mechanical watch by turning the crown clockwise until it blocks.STAINLESS STEELA highly resistant alloy composed of steel and chromium. It can be worked to resemble a precious metal. It is nearly impervious to rust, tarnish, and corrosion. SAPPHIRE CRYSTALSynthetic sapphire crystal is a tough scratch-resistant material, only diamonds could leave a mark. SILICON BALANCE SPRINGSilicon balance springs offer various advantages: immune to magnetic fields, temperature fluctuations, oxidation, aging, shocks, and maintains shape stability. WATER RESISTANCEYour timepiece is resistant up to 10 bar (100m) / 145 psi (328 ft).