ZENITH El Primero Flyback Chronometre, Ref. 03.1240.4001, movement no. 186574, circa 2000 A very attractive, large, water-resistant, automatic, stainless steel flyback chronograph wristwatch with guilloche silvered dial, applied radial Roman indexes and dart indexes, triple calendar and moon phases indications, 30-minute and 12-hour registers, constant second, tachymeter scale, leather strap and stainless steel Zenith deployant clasp. Fitted with a Cal. 4001, rhodium-plated, 31 jewels, column-wheel chronograph mechanism, flyback function, self-winding, blued steel screws, visible through the sapphire-set case back secured by six screws, sapphire crystal. Dial, case and movement signed. Diam. 41.80 mm. Thickness 13.15 mm. Accompanied by a Zenith presentation box. The flyback function, also called “Retour en Vol”, allows the pilot to quickly reset the chronograph hand to zero without stopping the mechanism. Fast and efficient, this function allows the pilot to make more precise position calculations during the flight.