Backdated, Backdating. Said of dies and struck pieces bearing a date earlier than that in which they were actually made. The practice of backdating was rampant in Early American coinage. America's first dated coins, the Willow Tree, Oak Tree, and Pine Tree coins were all dated 1652, but struck in 1653 until 1682. Some of the first coins struck at the fledgling Philadelphia Mint were backdated, including the 1795 half eagles (actually struck in 1797, Breen 6422-24).

The famed United States 1804 silver dollar was struck in 1834 (and as late as

1858) with backdated dies. One of these was in the famed King of Siam cased set of U.S. coins. Previous nonexistent dollars of 1801 through 1803 were also struck at this time, all backdated.

References:

NC8 {1988} Breen, p 430-433.