The 1852 restrike dollar struck in copper. These were deliberately struck for sale to collectors. Early 2001 articles in Coin World by Dave Bowers discuss practices by the mint in those years.
Silver restrikes of this date were known as early as lot 135 of Cogan's May 1859 Simon Gratz sale but the earliest occurrence for one of these copper pieces was in Cogan's April 1877 Jenks sale which may indicate that these were struck much later, in the mid to early 1870s, with another batch of silver examples. In copper, about a half dozen examples are believed to exist, one of which has been silver-plated.
Additional information can be found in "Silver Dollars and Trade Dollars of the United States" by Dave Bowers and Mark Borckardt.
It is unclear if these were struck from multiple reverse dies. The Mint had at least 2 "No Motto" reverse dies on hand in the 1870s.
Photo courtesy of American Numismatic Rarities.