Not technically an insulator, but many of you no doubt like this sort of thing as do I... Here's a porcelain-head street series incandescent luminaire with classic radial wave reflector in Westfield, NJ. Manufacturer is unknown but most likely is Hartford Faience Co. or Line Materials. It is currently in service along with a goodly number of others in Westfield and neighboring Cranford. All have long since been converted to multiple service however. The large, green glazed porcelain head provided insulation for the entering conductors from the series circuit for which these units were originally designed, necessary since series circuits utilized primary-class voltages. The steel radial wave reflector is enameled green on top and white underneath (and has some obvious rust holes!) The lamp now is most likely a 189 w, 2900 lumen PS-25 multiple incandescent. Further up on the ornate mounting arm (not shown) is a standard photo control. Note the brown porcelain wire holder insulator on the mounting arm - these carried the hv conductors to the lamp head rather than having the wires run directly through a hollow mounting arm. As can be seen the original conductors remain, running through the insulator although they are now connected to a 120/240 v multiple circuit. The insulator has a 'head' with a transverse hole as in the manner of a "house knob" or service wire holder, but also has a standard circumferential wire groove just below the head and double petticoats similar to ANSI Class 55-2 pintype units. These insulators were typically cemented to their pins probably to assure correct alignment of the hole with respect to the mounting arm axis. The bracket consists of a steel pin fabricated with a saddle base and U-bolt to clamp around the arm. These wire holders are typical ancillary hardware on most street series fixtures. The author is hoping one of these luminaries will turn up in surplus soon, as it sure would look sweet in the backyard! :-)