"Before the advent of a regular currency, transactions in the bazaars were made by weighing out lumps of metal, 'ganza', and in order to ensure that the correct amount of ganza was weighed out, the bullion merchants and shopkeepers used a series of weights which had been officially approved. The origin of these weights has not been established but it is thought that they were introduced to Thailand by the Burmese when they conquered Ayudhya in the sixteenth century, and as collectable pieces they are now commonly known as Siamese Opium Weights due to their use with the opium trade." (M. Robinson & L.A. Shaw, THE COINS AND BANKNOTES OF BURMA)