However, mass-produced metallic currency was difficult to be equalized in weight (at worst, the disparity was as large as almost twice) so Kai Yuan Tong Bao could not be said the standard of the weight of currencies.
ただし大量生産される鋳造貨幣というものは質量を一定に製作することは困難で（最大2倍程度のばらつきはある）、質量の基準が開元通寳というわけではない。