Framed Western picture by Charles Russell . Signed?

Hello, Thanks for looking at my auction site. I received this framed (with glass) 8 x 10 picture in a box of items I purchased at an estate sale in Colorado. I donn't know any thing about the name of this picture, or who Charles Russell was. I donn't know anything about art. Picture is not smooth like a print. Maybe litho ? In the lower left corner of the picture it has as a signature and date of 1890 in red and skull above signature. Unknown if signature is orginal or copy. I'll let you decide.

Happy Bidding!!!