The Lindbergh Hour Angle is one of the most iconic pieces in Longines' collection. It was originally designed in the 1930's by Longines and Charles Lindbergh ('The Lone Eagle'), it was an evolution of the Weems Second-Setting Watch which was designed in the early 1920's by Longines/Wittnauer and Captain Phillip Van Horn Weems. While the latter a rotating inner seconds scale to quickly synchronize the time as given by the watch with that of the radio signals (much more accurate at the time!), the former featured not only this rotatable scale, but also an intricate system of markings on both the dial as well as the rotating bezel. All these indicators served one purpose: to calculate the hour angle. With these additions, a reasonably simple watch was instantly transformed into a nifty navigational tool, aiding in determining the current longitude of its wearer.
Reference L2.601.4.11.2 has a stainless steel case of 38mm.