‘Worriedguy’ is close, but, this is what my book says….
Grade AA eggs are the fancy variety. They are uniformly sized & have as near perfectly formed shells as possible. When opened, an AA egg will cover a small area. The white will be thick and stand high. The yolk is firm & high.
Grade A eggs will cover a moderate area when opened on a flat plate. Their white portion will be reasonably thick and the yolk will stand fairly high. Both AA & A have ‘eye’ appeal.
Grade B eggs will cover a wide area when opened and will have a small amount of thick white and a greater amount of thin white. The yolk is somewhat flattened & enlarged.
Grade C eggs will cover a very wide area when opened. There will be little or no thick white surrounding the yolk. The yolk itself will be flat and greatly enlarged. Both B & C are used for sauces & cakes.