Shown respectively are the two known "signal" styles made by The Standard Glass Insulator Co. Boston. Joe recalls quite a few of these insulators strung upon Boston (MA) Fire Alarm circuit lines through the years. The first crop of them was liberated by him and Phil Harding in 1970. But that was the tip of the iceberg! The city system had them scattered all about their iron open-wire with other vintage aqua insulators including crown-embossed Brookfields in CD 133 and #134. There was very little clear glass! The Boston system was "picked over" through the late 1980s whereby very few if any Standard insulators may still remain (see note below). Of their pluckings in 1970, Joe and Phil soon found out that the inner skirt variety (CD 157.5) was far more common than the CD 138.2. In fact (Joe knew who the other "pluckers" were...no they were not from the Midwest!) and the latter style was found among a minority of the inner-skirt-less variety (CD 138.2). The ratio between the two was 8 to 1. (CD 157.5 to 138.2). Nearly all of the Standard's known have come from Boston. However it is known that electric utilities north of Boston have had them on their primary and secondary distribution circuits. In addition, Standard's were used on a municipal fire alarm system in Greenfield, MA (which is in the state's NW corner about 125 miles away). Nearly all are of a plain-Jane aqua but a few have been located in light ice blue (especially the CD 157.5). A further exception are a few in light green and these are of the aforementioned "signal" designs. Among the last-known installations of Standard insulators was along a two-pin Boston FD run through several backyards in Boston (1988). On each side of the backyards were fenced-off triple decker houses and in a tough neighborhood to boot! The insulators were mounted (2-apiece) upon buckarms (you linemen know that lingo!) making four insulators to the pole (there was just the one pole!). Since that location was inaccessible as described above and "protected" by man-eating dogs, a closer view was not possible. This incredible insulator-sighting was verified by one of Joe's collector friends who was working for the phone company at the time. And by binoculars! It is not known if this installation is still there.