Grade means any one of the officially established grades of potatoes, and size means any one of the officially established sizes of potatoes, as defined and set forth in:

(a) The United States Standards for Potatoes issued by the United States Department of Agriculture (§§ 51.1540 to 51.1556 of this title), or amendments thereto, or modifications thereof, or variations based thereon;

(b) The United States Consumer Standards for Potatoes as issued by the United States Department of Agriculture (§§ 51.1575 to 51.1587 of this title), or amendments thereto, or modifications thereof, or variations based thereon; or

(c) Standards for potatoes issued by the State from which the potatoes are shipped, or amendments thereto, or modifications thereof, or variations based thereon.