' Zenith 'El Primero' Ref 01.0500.400 a stainless steel chronograph wristwatch, circa 1990 dial: painted black with white Arabic numerals, subsidiary dials for constant seconds, 30-minute and 12-hour registers, aperture for date. Calibre: cal. 400-Z, automatic, 31 jewels. Case: stainless steel. Case number: 01.0500.400. Closure: later black leather strap and Zenith buckle. Dimensions: 38 mm diameter. Signed: case, dial and movement. Accessories: none