And be it further enacted, That from and after the passing of this Act all Instruments for or upon which any Stamp or Stamps shall have been used of an improper Denomination or Rate of Duty, but of equal or greater Value in the whole with or than the Stamp or Stamps which ought regularly to have been used thereon, shall nevertheless be deemed valid and effectual in the Law; except in Cases where the Stamp or Stamps used on such Instruments shall have been specially appropriated to any other Instrument by having its Name on the Face thereof.