It's a late 19th or early 20th century dress button bearing an Egyptian portrait. Some of these date from the Egyptian Revival period of 1860-90. Many were inspired by Victorien Sardou's play Cléopâtre , starring Sarah Bernhardt, in 1890. Finally, there was a major craze for Egyptian-motif items following Howard Carter's discovery of the tomb of Tutankhamen in 1922.