Hamilton Khaki Aviation Converter Auto ChronovsVario 1918 Medic Brass

The Hamilton Khaki Aviation Converter Auto Chrono is widely described as a large 44mm pilot's watch with a functional slide rule bezel. Reviewers note its well-finished steel case, featuring a robust satin-brushed finish with polished accents and chamfers, and a legible blue sunray dial with applied Super-LumiNova markers and old-fashioned hands. It is powered by the H-21-Si automatic chronograph movement, an upgraded ETA-based caliber with a silicon balance spring for anti-magnetic properties, offering a 60-hour power reserve. The watch is rated to 100m water resistance and features a bi-directional slide rule bezel with graduations printed under K1 mineral glass for scratch protection, which is easy to manipulate due to its deeply notched steel design. Some find the slide rule bezel complicated to use without a manual. One owner notes its character does not appeal as much as other slide bezel chronos.

Owners widely praise the Vario 1918 Medic Brass for its crisp enamel dial, easy-to-read numerals, and cathedral hands, noting the brass case develops an attractive patina over time. However, the soft brass scratches easily, and one owner found the lume to be poor. Accuracy varies, with one example running slow by about 10 seconds per day and another owner deeming the Miyota 82s5 movement just okay. On balance, owners rate the Vario 1918 Medic Brass highly for its unique dial and the evolving character of its brass case.