Pyrex Radio Antenna Strain Insulators, Eight US Made Styles

Full set of Pyrex US manufactured glass radio antenna strains. Beginning with the 3 1/2" Broadcast Reception Insulator, part #67007. This style shape was never changed during its thirty or so years of production.The 7 1/4" Amatuer Transmitting Insulator, part #67017 went through four versions. The part number was not changed. Each design change from the 7 rib to the 4 rib strengthened the insulator. The oldest 7 rib has the smallest eyes and least amount of glass by weight. The five rib has larger eyes with saddleways. It was improved to a fatter, stronger version. The 4 rib has reinforcing eye strutts and is the heaviest of the four.The 12 1/2" Strain Insulator shows similar changes. From the 11 rib with small eyes to the 9 rib with larger eyes and saddleways and, last, the 8 rib with reinforcing eye strutts. Dates of manufacture in the US range from the 1920s to around 1950. There are many shape, color and size variations but they are probably all foreign made. Corning licensed their products all over the world. These are all in very good condition, no cracks or missing glass. There are two very small pings in one. Can you find them in the pictures? Shipping reflects the 10 1/2 lb. of glass plus 1 1/2 lb. of packing materials.