Understanding USDA in shell grades.
U.S. No. 1
Similar varietal characteristics. Free from loose, extraneous and foreign material. Shells are clean, fairly bright, fairly uniform in color and free from damage caused by discoloration, adhering hulls, broken shells or other means. Kernels are well dried, free from decay, rancidity, damage caused by insects, mold, gum, skin discoloration, shriveling, brown spots or other means.
Loose Foreign Material
2%, including 1% passing through a 24/64" screen (this is also by weight).
10%, including 5% serious damage.
U.S. No. 1 Mixed
U.S. No. 1 grade, except that two or more varieties are mixed.
U.S. No. 2
Consists of almonds in the shell that meet the requirements of U.S. No. 1 grade, except that an additional tolerance of 20% shall be allowed for almonds with shells damaged by discoloration.
U.S. No. 2 Mixed
Consists of almonds in the shell that meet the requirements of U.S. No. 2 grade, except that two or more varieties of almonds are mixed.
Unless otherwise specified, 28/64" in thickness.