This is a limited edition and rare Alchron alloy Zenith El Primero Stratos Flyback Chronograph Striking Tenth, reference 24.2061.4057/67.C707. It has a black fabric strap with a push button double folding deployant buckle, and a scratch resistant anti-reflective coated sapphire crystal. It has an exhibition screw-down sapphire display case back secured with 4 screws, a screw-down winding crown, and rectangular chronograph pushbuttons. The 42mm diameter solid case, downturned lugs, and bezel are matte black Alchron. The watch is very difficult to obtain. This Zenith El Primero Stratos Flyback Chronograph Striking Tenth, reference 24.2061.4057/67.C707, was produced in a limited edition of 500 examples in Alchron a high tech material developed for the aeronautical and automobile industries. It has a magnetic permeability that's 50 times lower than steel, and it's corrosion resistant. It is a tribute to Alain Thébault There is a black ceramic inlaid unidirectional 60-min bezel with luminous Arabic numerals, and a red chronograph second hand that moves around the dial at 1/10th second intervals. The dial is black with "1/10th of a second" in red under the name, applied faceted SuperLuminova trapezoidal hour markers around a white minute track, and luminous baton hands. There are three white subsidiary dials with brushed steel rims, including a minute totalizer at 6 o'clock, a constant seconds dial at 9 o'clock, and a 50-hour power reserve regulator at 3 o'clock. There is a date aperture window at 6 o'clock. It's water resistant to 100 meters, 330 feet, and the 13.7mm thick case, dial, and movement are all signed. The mechanical automatic self-winding Zenith El Primero caliber 4057B movement is rhodium plated with fausses cotes embellishment and a Côtes de Genève stripe pattern on the oscillating weight. It's constructed with 31 jewels, 326 components, and the mechanism oscillates at a frequency of 36,000 vph (5 Hz). The auction is for the watch only and DOES NOT come with the original box or papers. It will be supplied with a watch box. The watch was purchased at Bicester Village in the UK from new. Hardly worn.