(1) Every instrument written upon stamped material is to be written in such manner, and every instrument partly or wholly written before being stamped is to be so stamped, that the stamp cannot be used for or applied to any other instrument written upon the same piece of material.
(2) If more than one instrument be written upon the same piece of material, every one of the instruments is to be separately and distinctly stamped with the duty with which it is chargeable.