Since the 1950s, IWC Ingenieur has been one of the most popular models of the Swiss watch manufacturer. Initially represented by two models, various versions are now offered for different purposes. All models have a timeless classic case in common, which is pleasantly large but not ostentatious. Compared to other models in the upper segment, the housings are pleasantly flat. This makes it easy to wear the watches under shirts and jackets. IWC's engineering models are available in various material combinations. This ranges from stainless steel cases for the standard models to cases in pink gold for upscale models. Some of the undersides are made of crystal glass, through which the mechanics of the watches are visible.