I too, have one of the dirty dog prints. It has Hau forte originals in top right hand corner, Copyright by O'klein, Chamarande{S &O} in Left top corner and some kind of french Chacum son Soiur, I think in bottom left and some illegible signature in bottom right. The picture is very detailed and looks to be pen or ink drawing with light color over some of the dogs. It is signed in pencil. Can anyone tell me who else may have signed these prints besided O'klein? I think they are so funny... Would like to have more. LM