orangoutans

Hello, Perhaps a kindly member may help me out on this item. A good friend has an original Estonian pilot's badge (eagle clinching a tri-colour triangle) and is wishing to sell. I like the badge but have absolutely no idea of a mutually fair price. The threaded cap screw to the rear is embossed with the maker's name Roman Tavast and Tallinn. Any assistance would be most appreciated, also the time of issue etc