they are similar, but I don't think they are the same dress. eh..ok. maybe. The one from Henrik's birthday doesn't have quite the same flounce, IMO. Plus the dress from Germany has two buttons on it. Granted, they can probably be removed but...I don't know. The more I look at it, the more I think they're similar. But I'm not convinced they are the same dress, but they very may well be. Only Mary knows really.
(Forgive the awful dodge effect that I used to lighten the pictures.)
All three pictures were originally from the Crown Princess Mary Board.