All shell eggs of chickens sold or offered for sale by any person, firm or corporation shall meet at least one of the consumer grades for shell eggs established by the United States Department of Agriculture under the federal Egg Products Inspection Act, as amended from time to time. Nonconforming edible eggs of chickens shall be sold as “undergrade eggs”, or as “checks”, “cracks” or “dirties”. The final determination as to meeting these grades shall be made by candling.