This is among the first mercury vapor fixtures that replaced "clunky" and "gumball" looking incandescent street lights in the early 1960s. The fixture shown has its lamp in the "open" as did Westinghouse and GE from around 1961-68. Beyond then, plastic or glass refractors were used. Most mercury vapor streetlights (bluish-white colored ones) are a rare nighttime scene today. High pressure sodium (HPS) streetlights (the yellowish ones) have overcome the aforementioned classics because they are twice as energy-efficient as the mercury vapor lights. However, there is increased public comment about such "yellow" streetlights as being hideous and that the classics should emerge upon the American landscape not only by daytime aesthetics(reproduction fixtures) but as white (metal halide) lighting sources which are nearly as energy-efficient as HPS. For more information about vintage streetlights see: http://www.groups.yahoo.com/group/vintage_streetlights Thank you.