This mixer was featured in the 1949 Willys Overland Equipment Book. It was manufactured by Hertzler and Zook, a company established in 1899 out of Belleville, Pennsylvania, that manufactured an array of machinery and farm implements. There are still a few catalogs left out there, such as this 1926-27 catalog for sale at Abe Books.
Read more about the company here: http://vintagemachinery.org/mfgindex/detail.aspx?id=439&tab=0