LONGINES CAL.13ZN FLYBACK CHRONOGRAPH STEEL Longines, No. 5866164, case No. 21514, Made circa 1945. Fine and rare, stainless steel wristwatch with round button flyback chronograph, register and tachymeter. Three-body, polished and brushed, concave lugs, stepped bezel, snap on case back. Black with printed Arabic numerals, subsidiary dials for the seconds and the 30-minute register, outer 1/5th seconds/minute track with five minute Arabic markers, outermost tachymeter scale. Cal. 13 ZN, straight-line lever escapement, monometallic balance, shock absorber, self-compensating Breguet balance spring, index regulator.