These are all "Gong" whistles. They were not as common as regular whistles but many survive. They are different from regular whistles because gong whistles have a common bowl or base. The bowl has two steam slots on each side. One slot blows one bell ( cylinder ) and the other slot blows the other bell. Steam comes from the whistle in two directions. There are two types of gongs. U.W.M. of Worcester, Ma. made the vertical type with the copper bells. Sinker-Davis, of Indianapolis, In. made most of the all cast iron horizontal gongs. They were made in sizes from 4 inch bell diameter up to 12 inch bell diameter. All of the U.W.M., 3bell, gongs shown here are 12 inch diameter.