From www.foodreference.com...
Ming Dynasty eggs, fermented eggs, ancient eggs, century eggs, thousand year old eggs, and hundred year old eggs. These are all names for the Chinese preserved (usually Duck) eggs. They are really only about 50 to 100 days old. The eggs are covered with a coating of lime, ashes, salt and rice straw and buried in shallow holes for up to 100 days. The lime petrifies the egg making it look very old. The yolks turn amber to black with a creamy dark green yolk. They are eaten uncooked with soy sauce and minced ginger.
I think I will stick with the chick.