Benrus Watch Company was an American (family run) company. It was founded in New York City in 1921 by three brothers - Benjamin, Ralph, and Oscar Lazrus. The ambitious brothers were Romanian immigrants. The name "BENRUS" was a combination of Benjamin Lazrus first and last names. Hence "BEN"jamin laz"RUS". The early 1920's was a turbulent time for the watch industry as pocketwatch demand was cut in half - this was due to the rising popularity of the wrist watch. The three young brothers saw an opportunity to begin a wristwatch company that produced moderately priced watches for the common-man.

The original company headquarters were located in the Hippodrome building on 44th street in Manhattan. While some watch assembly took place there, but the bulk of the manufacture took place in Switzerland. Benrus owned a factory in la Choux de Fond where watches were assembled. This was run by the first woman to run a major Swiss company. At the time all Swiss watches and parts were controlled by the Swiss cartel who provided Benrus with the movements and parts. Benrus also had a factory in Waterbury CT which is where they made the cases for Benrus watches. The company would later own factories in France, St. Thomas, and Virgin Islands in the late 50's early 60's.

The Sky Chief was designed for and worn by aviators from the early fourties until the late sixties. Benrus was official supplier to many commercial airlines during this time period, including specifically Colonial, Delta, National, Northwest and KLM (as you can see here). The movement was a modified Valjoux 71, Valjoux 72, Valjoux 72C (=calendar) or a Venus 178. This particular Sky Chief has a 17 Jewel Benrus movement Cal.VZ3 (first generation of the Valjoux Cal. 72 with breguet hairspring). Number of the movement KII2/677-Model VZ3-AXZ. Black dial with luminous numbers and hands.  30 minute counter at 3 o'clock, constant seconds at 9 o'clock and 12 hour counter at 6 o'clock. Outer 1/5 Seconds graduation.  The case was made by the famed Swiss case and bracelet maker Gay Frères.

A nice Benrus WWII gadget story can be found here

The special markings at 4, 8 and 12 minutes on the minutes dial of the chronograph is subject to much debate. The most plausible explanation for these markings to me is that it can be used to navigate in flight. The basics are that the changes in altitude for celestial bodies was given in one and four minute intervals. To get a solid navigational fix take 3 sights at 4 minute intervals with the help of an Astro Compass. You take a sight which takes about 2 minutes, then you have 2 minutes to write your notes and reset the sextant. Then you do it again exactly 4 minutes after the first sight. Then a 3rd time, all using the same celestial body (sun during the day, certain stars at night.) Depending on turbulence, you hope to get at least 2 good sights. These instructions are written in the worksheets and HO 249 tables used by B52 bombers. Some Sky Chiefs seem to have these markings at 3, 6 and 9 minutes, but as far as I know these dials are not original but are fake dials to replace the damaged original ones.

Dial has loss to the finish in spots but is still in good condition. Dial is Signed Benrus Sky Chief, Swiss. The watch is 35mm in diameter excluding crown x 43mm top to bottom. The Sky Chief is now one of the most popular type from Benrus and sought after by Benrus collectors over the world.