This is a mercury vapor street light fixture installed in the 1950s. The pole-top insulator bracket arrangement most likely came *well* before that. The ballast for the street light can be readily seen. The street light fixture is 250 or 400 watts and is within a cast alunimum Revere Manufacturing Co. fixture (made in Chicago). This probably was a trolley pole and the bracketed insulators likely are original. The one on the left is a glass or porcelain version of the CD 287. Photo courtesy of LGnet.