Hently, a 1680 case that said an indebted merchant owed his debt to the person who had lent him the money, not to a debt collector who came around bearing a note.
In exchange for the stock the grantor takes back a promissory note, again bearing a government-specified rate of interest (currently less than 1% for a nine-year note) that locks the value of the stock in at the time of the transfer.