The development on the W140 began in 1981, with official introduction originally set in September 1989. Several different design proposals were studied from 1982 until 1986, when a definitive design proposal by Olivier Boulay was selected on 9 December 1986. Several engineering prototypes were evaluated from early 1987, with the final exterior design locked in September 1987. The design patents were filed on 23 February 1988 in West Germany and 23 August 1988 in the United States. The lead designer Bruno Sacco attributed Jaguar's XJ40 sedan and BMW's E32 7-Series as a major influence in W140 design. The initial exterior design proposal called for the two different cooling grille designs to denote the lower and upper model, similar to the idea of round and rectangle headlamps on the W123 (1976-1985). Innovative metal-forming technology allowed the extension of the engine hood/bonnet to the front bumper, with the grille placed inside the extruded metal. The W140 became the second model after the R129 (1989-2001) to have this extruded metal grille.