The first information that we have on metal churns is per some hardware information dated 1910 that listed metal churns in sizes, 1, 2, 3, 4, 6, 8, 10 gal sizes. In a 1911 catalog, they listed additional sizes of 16 gal and 28 gal. The first metal churns had straight edges but we found through some information that the edges were changed to round to be easier in cleaning. You can tell the size of the churns by looking at the numbers on the metal part of the top. If it states 130B, the first number tells you that is a one gallon size, if is 230B, it is two gallon size and so on and so on. The larger sizes came with motors or were manual. The one-gallon is the most desirable size to own. We have not seen a one-gallon with rounded edges but who know it may be out there.