Our ducks had been laying chicken sized eggs for a couple days when my daughter brought in a biggie like that. I was sure it was just (finally) the size I thought a duck egg should be. Imagine my surprise when it was double yoker! They are really neat.
We lost one of our girls to a fox and the next day one of her coop buddies laid this whopper. The other egg it is next to would be considered large, we couldn't even close the egg carton. My 13 yr old son said "That HAD to hurt!"