This was in the posession of the GIRD/Smith family. John Gird (which one I don't know) wrote on the outside of the paper that he did not know how it came to be in the Gird family posession.
It is the purchase of one Male Negro Slave, named "Frank" - 1784. The seller was Stephen Hix ( Hicks) of Queens County.
 
The buyer was Richard Smith of Huntington, Suffolk County, "Island of Nassau"...it says.
The amount paid for Frank was 60 pounds to "Richard Smith" & "his heirs...forever".
Dated:  6th October, 1784

The right scan is actually the Bill of Sale; the other scan is the outside of the Bill of Sale with the words of John Gird written across the paper.