Knox
The Knox Porcelain Corp. from Knoxville, Tenn. was founded in 1923. "In September 1975 (Knox) was bought by Porcelain Products Company".
U 318's
Similar to a U 301 but with a more rounded dome
U 285A also displayed on PP Inc page
Characteristics:

Color(s) --- streaked sky blue, cobalt blue, chocolate browns, whites

Pinhole(s)
--- glazed with 2 Radio Treated (white ink stamped U 318, brown RT U 318

Pinhole Top(s)
--- rounded to flat dime sized depression

Fire Rested
--- petticoat

Wet/Dry Processed
--- wet

Marking(s)
--- 6 incised om skirt "KNOX" with stylized triangle replacing the "O" in KNOX. 1 ink stamped on skirt, black ink.