Antique Mystery Painting - Native American subject? Seeking help dating the painting and/or identifying artist

My dad purchased this from an estate sale. He seems to think it's quite old, and believes it depicts a Native American. It is signed in the upper right corner of the front. I cannot tell if the first initial is a lowercase "J" or a "G", or perhaps even some other letter. I have found a few artists with the same last name, but could not find a signature like this one. Also, many sites want to charge for information. I am hoping someone can provide a bit of insight into the subject and perhaps even identify the artist. Thank you kindly for looking.