This section is from the book "The Potato: A Compilation of Information from Every Available Source", by Eugene H. Grubb, W. S. Guilford. Also available from Amazon: The Potato: A Compilation Of Information From Every Available Source.
Disqualifications: For show or first three market grades. Screen less than one and seven eighths inches in clear. Many knots. Very deep eyes or very irregular shape. For show, any mixture of varieties; for market, more than 5 per cent. of same color or 2 per cent. of different color. Color mottled, splashed, blue or purple. Muddy. Over 15 per cent. scabby or wormy, or 1 per cent. unsound. One fourth hollow. Sacks not neat; strong, uniform in size. Sacks not securely sewed with standard sack twine.
Trueness to name and type required, but judges are instructed to favor improvements in type. No red potato to score as high on color as a white variety; no deep-eyed or long potato to be scored as high on shape as if round and smooth.