It's probably a long shot but I use to have a set of three prints in poster format of America Indian Chiefs they were
Sitting Bull , Red Cloud , High Horse
I unforutnetly don't have images I can post but I recall part of the signature on the print being Pope
They were all shoulder length with the respective Indian in headdresses and a different scenes in each print from buffaloes to an Indian rider in the desert . Any information you might be able to supply I'd be very great full for