Every vintage mechanical wristwatch was designed for a purpose.  Sometimes it was based on style, others on function.  The Tissot Navigator was blessed with both.  

Designed for military wearers - probably pilots, because of the inclusion of the world timer bezel - this Tissot Navigator T12 is a rare and interesting execution of a 24-hour mechanical watch.  While many military watches included 24-hour time by supplementing the dial or bezel with additional numerals (adding a 13 at one o'clock, 14 at two, and so on) the Navigator went full bore, producing a 24-hour dial and movement combination.

The result is incredible. 

The 24-hour time is also ingeniously reflected in the two-tone dial design.  The top half of the dial, colored in light tan, corresponds to the most common hours of light – 0600 hours to 1800 hours, or 6 AM to 6 PM.  Conversely the bottom half, shaded in a grey-brown, corresponds to hours of darkness - 1800 hours to 0600 hours, or 6PM to 6AM.  

With a robust automatic movement set into the gorgeously big compressor-style case, complete with date and inner rotating world-timing bezel, this beaut is 2 parts function, 1 part sex.  And, with the addition of a date function, this watch goes from being wearable militaria to every day wearer.  Throw in the original Tissot-signed steel bracelet and you have a game-changing piece of vintage horology at a hell of a price.