Speculum metal metal mixtures usually contain two parts copper to one part tin along with a small amount of arsenic, although there are other mixtures containing silver, lead, or zinc. The knowledge of making very hard white high luster metal out of bronze-type high-tin alloys may date back more than 2000 years in China although it could also be an invention of western civilizations. Such metals were used in sculpture and to make more effective mirrors than the more common yellow easily tarnishing bronze mirrors. In that era mirrors of speculum metal, or any precious metal, were rare and only owned by
Metal and Machinery Workers Industrial Union Reuther Library in Detroit. Metal and Machinery Workers Industrial Union The Metal and Machinery Workers Industrial Union No. 440 (MMWIU) was a labor union in the United States which existed between 1907 and 1950. It organized workers in the manufacturing industry and was affiliated with the Industrial Workers of the World (IWW). The earliest recorded local of the MMWIU was in Bridgeport, Connecticut in 1907. A number of machinists' locals were also active under the IWW around that time, which dated from a period when a large number of craft union locals were switching their affiliation to the IWW, and