"The weights are precisely made, well polished and systematic (though unfortunately not inscribed with any Indus characters, which would have helped scholars to decipher the script's numerical system). Unique in the ancient world, the Indus weight system does not correspond to any of the weight systems used in Mesopotamia or Egypt. It has left a remarkable legacy in India. It provided the weight standards for the earliest Indian coins, issued in the seventh century BC. It was identical with the system used by the first Gangetic kingdoms around 300 BC (just prior to the reign of Asoka). And it still functions, in the third millennium AD, for weighing small quantities in traditional markets in both Pakistan and India." (Andrew Robinson, The Indus, p. 64).
Indus weight images copyright and courtesy Jameel Center for Islamic and Asian Art, Ashmolean Museum, University of Oxford