To determine the value of a Ray Harm print, appraisers consider the item's issue date, edition, issue price, size and common value found on most global markets. Also, because Ray Harm is widely known for his naturalistic depiction of birds, these works are considered more valuable than his others.
Ray Harm's prints appreciate in value over time, and older items are sometimes worth more than newer items. However, a print of an American bison from 1978 is actually worth more than Harm's entire African Sketchbook from 1973. This is because there are fewer prints of the American bison available, and they bear the official signature and numbering from the artist himself. A Ray Harm print that features a bald eagle family and bears an issue date from 1963 as well as a signature has a current market listing price of $850 as of May 2015.
Appraisers also seek more mundane features such as the size of the print and its condition and current protected state. An item that is framed or otherwise protected for much of its lifespan is also typically in good condition and is, therefore, more valuable as a result. Size doesn't always affect the value, which is often more reflective of current market desirability among buyers.