In the early 1950s, Breitling collaborated with the AOPA (Aircraft Owners and Pilots Association) in order to make the slide rule of its Chronomat even more relevant to pilots. The end result, the Navitimer, was a well-conceived tool watch with outstanding legibility. The very first examples came with an all-black dial, but eventually the sub-registers became white to increase the contrast and make it even more legible. Similarly, the AOPA logo was replaced with the twin-jet logo, and the beaded bezel also evolved. Despite these minute cosmetic changes, the Navitimer remained pretty much identical through the years, proving how well executed its first draft was. This model has white sub-registers. Signed on dial, crown, case-back and movement. All stainless steel. Snap-on caseback. Case diameter: 41mm excl. crown, 44mm incl. crown. Crown diameter: 6.5mm, non-screwdown. Distance between lugs: 22mm. Distance across lugs: 48.5mm Movement is Venus cal. 178 integrated chronograph with castle wheel, manual wind, 17 jewels, 18,000 bph, Glucydur balance, Nivarox 2 hairspring. Incabloc shock protection.The power reserve is 46.5 hours (measured—full wind to stop, chrono off).