Oak Mission style slant top desk

I have owned this desk for about 20 years and would like to sell it. A family member bought it in the early 1980's in Southern California. He thinks he paid around $1,000.00 for it. It is an early american mission style piece. He thinks 1920's. The bottom of the legs have a little wear and there is a small sharpie mark on the middle drawer (not even visible in the picture). Does anyone have any idea of what this is worth? I would like to sell it.