Patek Philippe produced two steel versions of the Ref. 3700. Ref. 3700/01, produced between 1976 to about 1981 featured a straight, integrated bracelet. The bracelet of the Ref. 3700/11 tapers slightly more. The firm produced the Ref. 3700/11 from 1981 to 1990. Most commonly found in stainless steel, the bi-metal steel and gold version of the Nautilus is much rarer and arguably undervalued, compared to the all-steel version.
For a note on the Nautilus, please see lot 83.