Sparton, Stewart-Warner, and GMI all produced motor-driven horns (Sparton's was their Model BF) for the first half or so of the 1932 model year and the same horn was used on all U.S.-produced vehicles. When the ******** horn was adopted as a running change, Sparton was evidently the sole supplier. Again, the same horn (designated Model CF) was used on all vehicles and was carried over for most commercial vehicles and big trucks through the 1934 model year with different mounting brackets depending on the application.