Welcome to Just Answer and thanks for your question. The first thing would be to determine if it is by Bert Seabourn or some other artist. Mr. Seabourn refers to himself as an expressionist artist who paints Native American subjects as well as many other things. Here is his web site: http://www.seabournart.com/index.html
If it is a numbered copy of a limited edition it may be worth more than you paid for it if it is truly a Bert Seabourn. Someone would need to look at it in person to verify authenticity.