The Hobby Protection Act of 1973 only gave blanket protection to coinage produced by the U.S. Mint , by proclaiming that ANY reproduction of a lawful U.S coinage design required the addition of the word COPY to the design of such.  This is not the case with commemorative MEDALS(which do not have a monetary denomination indicated in the design)produced by the U.S. Mint, which continues to make souvenir reproductions of classic historical medals such as those originally cataloged in R.W. Julian's "Medals of the United States Mint, The First Century. 1792-1892".  As a general rule,  the majority of these medals STRUCK in the late 18th century or throughout the 19th century were of copper composition, and should display a deep mahogany color on the surfaces. The modern (20th century) reproductions of these medals are CAST in bronze, and will display a pale gold color.  Typical examples of U.S. Mint reproductions that have been apppearing on eBay recently(and either deliberately or mistakenly misrepresented) are the 76 mm 1865 dated Cornelius Vanderbuilt medal, and the 62 mm 1882 dated Great Seal of the United States Centennial.  The genuine contemporary issues of these medals are of significant value, so caution should be exercised when assessing the authenticity of any offering that does not have the appearance of the above description for original issues.