Wayne Allen very recently found a couple of these white porcelain receptacles that are identified for use with (series) street lights. My friend Joe Maurath is a long-time purveyor, collector and researcher of vintage streetlights. I am showing this photo of the completed socket assembly (which mounted in a metal fixture head) along with the "plug-in" porcelain socket that these were used with. Also shown towards the bottom of my picture is an example of a 6.6 ampere street series light bulb. For more information about old-time streetlights visit Joe Maurath's website: http://www.vintagestreetlights.com and his group on Yahoo: http://groups.yahoo.com/group/vintage_streetlights