Why eagle odnogolovy?
 

http://www.lot-tissimo.com/de/cmd/d/...73/auk/57/p/4/
Dear not prompt, but why an eagle odnogolovy?

I faced similar. Clearly Prussian eagle with orb and scepter. In numismatics more common. In this case, probably a helmet Libau Regiment. In Wikipedia, there is about him - look.