Porcelain Threaded Pintype Insulators from the United States

Porcelain pintype insulators in the United States began to appear in volume around the turn of the century, and quickly replaced their glass counterparts for electrical power distribution.  Porcelain was never as popular as glass for communication wires, but the strength and durability of porcelain was ideal for the power industry.  single piece porcelain insulators are called unipart insulators, and are identified in the hobby with U numbers.  Unipart insulators include true single piece insulators, insulators that are made of multiple porcelain units that are "glued" together with glaze (Known as glaze-welds).  Jack Tod developed the U numbering system, and there is a highly recommend reference book available as follows:

Porcelain Insulators Guide Book For Collectors (Unipart Pin Types)

Pony and exchange styles as follows: U-11A, 12, 13, 12, 38, 3, 32, 59, 48A & 65

Some early styles made by (or for) Fred Locke: U-441, 939, 383, 927A, 447, 608A, 339B, & 669

Additional early styles: Imperial U-924 & 927, Thomas U-939B & 928, Imperial U-940B, Pittsburg U-395, & Imperial U-940A

Telephone transposition styles: U-211, 209, 206A, 217A, 206, 206, & 202A

Additional Styles: U-189A, 521, 109, 540, 356B, 154 & 780

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