Available at Cowan's American History Auction.
Here's the auction house description:
Approx. 1.5 in. square, stamped copper with arched *Charleston* above 808 over Servant, over 1855. This particular tag was dug in December 2007 by a well-known Charleston, SC digger, William L. Hunt, and is accompanied by a letter from Hunt, authenticating the tag. According to Hunt, the tag was also certified by Dr. Harry S. Hutchins, Jr., who published the guide on Slave Tags. This tag was featured in several magazines including Western Eastern Treasure Magazine, The American Digger Magazine, and The North and South Trader Civil War Magazine.