Dear David - Greetings and congratulations on your acquisition of this pastel on paper by R. C. Gorman. This is an excellent original, great size and popular iconography. Similar seated Native American women are offered at auction a couple of times each year and pieces conform to the same general dimensions and scale as yours see a range of between $4200USD to $5500USD.
Do let me know if you have any follow-up questions and have a wonderful evening.

Sincerely,

Erin-Marie