The Presidential $1 Coin Program honors former presidents of the United States. Beginning with George Washington, each year the U.S. Mint releases four new coins with portraits of the former presidents on the obverse. The reverse of the coin shows the Statue of Liberty. The program stipulates only deceased presidents are eligible to be honored in the program. The motto "In God We Trust" was controversially placed on the edge of the coin. Some 2007 Presidential dollars were mistakenly issued without lettering on the edges, and the U.S. Mint then decided to place the motto on the obverse. Presidential dollars have a pure copper inner core and an outer layer made of 77% copper, 12% zinc, 7% manganese and 4% nickel. They measure 26.5 mm in diameter, and each weighs 8.10 grams.