``U.S. No. 1'' consists of walnuts in shells which are dry, practically clean, bright and free from splits, injury by discoloration, and free from damage caused by broken shells, perforated shells, adhering hulls or other means. The kernels are well dried, free from decay, dark discoloration, rancidity, and free from damage caused by mold, shriveling, insects or other means. (See Sec. 51.2954.)
(a) At least 70 percent, by count, of the walnuts have kernels which are not darker than ``light amber'' (see color chart), and which are free from grade defects: Provided, That at least four-sevenths of the above amount, or 40 percent of the walnuts have kernels which are not darker than ``light'' (see color chart). Higher percentages of nuts with kernels not darker than ``light amber'' which are free from grade defects and/or higher percentages with kernels not darker than ``light'' which are free from grade defects, may be specified in accordance with the facts. (See Sec. 51.2954.)
(b) Size shall be specified in connection with the grade. (See Sec. 51.2952.)