 The reasons for this change are not clear; Byzantine chroniclers, however, suggest fiscal motives, reporting that Nikephoros collected the taxes as before in the "histamenon" while paying back with the "tetarteron", which was officially rated as equal in value to the full-weight coin.Initially, the two coins were virtually indistinguishable except in weight.During the later reign of Basil II (), the "tetarteron" began to be minted in a thicker and smaller form, while the "histamenon" became correspondingly thinner and wider.