Pictured on this page are eight fraudulent birdstones made from porphyry and other hardstone materials. Which fake did you select on page 19 as having a shot at being authentic? In the author's opinion, and based only on the photograph, it would be the example in the upper left corner on page 19.
Eight more fraudulent birdstones made from very colorful porphyry. The quality of these fakes range from goofy (left column, second from top) to pretty good (right column, second from top).