U-990: USA
4 1/4" X 4 1/4" (107mm X 107mm)
No markings
{Southern Porcelain Co.}
Picture courtesy Elton Gish
U number assignment by Jack Tod
Return to the National Insulator US Unipart page
4 1/4" X 4 1/4" (107mm X 107mm)
Return to the National Insulator US Unipart page