This style of shackle was used during the eighteenth century, and similar looking shackles were discovered in the wreckage of the Henrietta Marie, a slave ship which sunk off the coast of Florida in 1700. The design of these shackles is consistent with those employed during the notorious ”Middle Passage,” the only type of shackles that can be verified as a slave shackle. All other 19th century shackles, unless accompanied by a letter of providence, could be said to be jail house or chain gang shackles.