What are the grading standards for soybean?

The grading established by the Federal Grain Inspection Service (FGIS) for the USA are the typical standards. Soybeans are divided into two classes based on color: yellow soybeans and mixed soybeans. Each class is divided into four numerical grades (US No. 1, 2, 3, and 4). Six factors are considered in assessing grade designation: test weight, heat damage, total damage, foreign material, splits, and soybeans of other colors. Although moisture, protein, and oil contents are not part of the official grading standards and do not affect the numerical grade, they may be specified on contracts in some markets.

Source: The Production And Genetics Of Food Grains