If you pre-order it from Game you get Prussian Death Hussars, if you pre-order it from Bol.com you get etc. If you preorder it from you get the USS Constitution. Besides the units you also get a special map with all the commercial sea routes.
Besides the extra 6 elite units exclusive to this collector's edition, which will be unlockable through steam, depending from which retailer you pre-order there are other additional in-game exclusive units.
