Help needed with Prussian Iron Cross 2nd Class

[dutchbarge]

Hello,  I'm a bit confused (seems my constant state these past months) about the correct wearing of  the Prussian Iron Cross 2nd Class. I've seen the cross worn on a tunic suspended from a ribbon either singly or on a medal bar (Ordernspange) with other medals, the ribbon only on a ribbon bar (Bandsprung) either singly or with other ribbons or the ribbon only worn diagonally in a buttonhole.  I've never seen a soldier's tunic with ribbon(s) worn diagonally in the button hole (and all that I have seen worn thus were sewn in place) that also displayed on the tunic the medal(s) represented by the button hole ribbons.  Somehow is doesn't seem correct to be wear more than one example of a decoration at a time.  Perhaps each way of wearing the cross was particular to the order of dress (ie. medal bar/ribbon bar on dress uniform, buttonhole ribbon on service dress)?  Any help will be much appreciated.  Cheers, Bill