native american portrait print circa 1900

I've had this print for over 30 years and have never found the original painting/image from which it was copied. it was found in Portland Oregon and it bears the label of the historic local department store's artistic framing service. in all my years of searching for who painted it and where it resides I've shown it to numerous painting and native American collectors and no one had ever seen it or recognized the artist and extensive internet searches have never turned up any likeness. the image was crafted by an obviously gifted painter. the subject appears to be from a plains tribe. I did find a single poorly done Sunday painter oil painting copy of the image here in a Portland antique store that looked to date from the 20's so perhaps the original was hung here on display in the pacific northwest at one time. the measurements are approximately... image 11"x 14"...frame 14"x 19".
interested in any opinion anyone might have.