(L to R): CD 187's in purple, smokey purple and smoke.
Interesting insulator design that enabled telephone companies to double up the number of wires without changing out the pole or crossarm. The crossarm was modified to accept duplex pins that are threaded on both ends. With a threaded end above the crossarm that took a pony or other telephone insulator and a threaded pin end under the crossarm that accepted a Brown's pony, telephone wires could be extended above and below the crossarm.
These CALIFORNIA Brown's ponies are displayed upside down from how they are used. They were molded with a glass plug/covering over the pinhole that had to be punched out after the insulator was annealed. Not pictured is the roughness of the glass around the pinhole where the plug was removed. I have found two different embossing height variations in these duplex insulators. The purple ones in the photo have 5/16ths inch high embossing and the smoke has 6/16ths inch high embossing.
This insulator shape is pretty poor to display California colors, so the color of the glass needs to be strong. I am looking for a sage green and yellow example.