In 1976, Karmann submitted the prototype of a 3 Series E21 convertible to BMW, but it was Baur's design (top-cabriolet) that was preferred. The Series 3 E21 was however the subject of other more or less confidential transformations: Reinhard Peters, Lumma Design or American Coach Builders. One can also mention the AGM (Netherlands), the Hornstein (Germany) and Bradford (USA).