From the time when coins was first used in India in about 600 BC, until the time of the Mauryan Empire (321 – 187 BC) the basic form of coin was a silver piece punched by one or more stamps bearing deigns of a largely pictorial character.
The Mauryan Empire coins were punch marked with the royal standard to ascertain their authenticity. The Arthashastra, written by Kautilya, mentions minting of coins but also indicates that the violation of the Imperial Maurya standards by private enterprises may have been an offence. Kautilya also seemed to advocate a theory of bimetallism for coinage, which involved the use of two metals, copper and silver, under one government. The Mauryan rule also saw a steady emergence of inscribed copper coins in India as evidenced by Tripuri coins in Ashokan brahmi script and various pre Satavahana coins dated 3rd-2nd century BC in Deccan.
The Mauryan coinage consisted almost exclusively of silver karshapanas of roughly 3.4 gm, a series that continued the Magadha karshapana series. Almost all Mauryan coins have five punches, as did the Magadhan coins before them, namey a sun, a “6-arm symbol” and three others. Some of the last coins in the series also had a punch on the reverse of the coin.
Over time, the flans became smaller and thicker. Mauryan Empire also introduced for the first time in India square shaped copper coins with punch marks. The economy must have been very prosperous, as the coins seem to have been minted in the millions.