It's marked on the base with Wellsville China Co., Wellsville Ohio, 59 (or maybe 58 - it's not very legible). The 59 refers to the date made - 1959.
Approximate measurements:
Height 2 1/2"
Diameter of opening, not including handle 3"
Very good condition: No chips, cracks, utensil marks, or crazing. There's a little pitting from wear on the rim and handle, but excellent condition otherwise. Please see photos for details.
A wonderful piece!