History of Technology in India, Vol. I: From Antiquity to c. 1200 A.D. v1.c13.s2.t10.3

v1.c13.s2.t10.3

The Silver coins from Gupta period has been found to contain 27 to 28% Cu i.e. corresponding to the near Eutectic composition of the alloy. As shown by Ag-Cu phase diagram in Fig. 45 the Eutectic alloy (Ag-Cu) containing 28.4% Cu has a melting point of 779°C only i.e. much lower than any of these pure metals. Kautilya’s Arthaśāstra describes in great detail the process of manufacture of these alloys and the techniques applied for minting coins which used to have a definite weight. In the beginning these coins were square in shape and their weight was controlled by cutting the required piece of metal from one corner. When the minting of circular coin was begun its weight was controlled by taking a weighed quantity of the alloy and punching out dimensionally controlled coins having the desired punch marks. The study of the punch marks on ancient coins have revealed high level of craftsmanship in the preparation of punching dies. The study of coins of the medieval and latter period have indicated the use of rolled sheet of controlled thickness.