A person may not sell, offer to sell, or deliver any shell eggs not properly designated in respect to quality and size standard. When shell eggs are sold or offered for sale, the designation shall be plainly and conspicuously shown on the container and in the offer to sell, and if the shell eggs are loose, by a sign placed on or near the eggs. Any shell eggs not designated as United States Department of Agriculture Grade B shall be presumed to be United States Department of Agriculture Grade A in allowing tolerance for quality.