The 2nd edition has a quite big golden label for "Best historical simulation 2006" on the front box.

There is no difference between the so-called Rio Grande and Histogame edition, since Rio Grande just distributed the Histogame edition in USA.

There is a difference between 1st and 2nd edition, most important to name is the control marker die cut sheet.

For further explanation of all differences, see here:

http://www.histogame.de/friedrich/e_zweitauflage.html