from festive (such as Bacchanalian scenes) to Buddhist-devotional. Uncertainties in dating make it unclear whether these works of art actually depict Greeks of the period of Indo-Greek rule up to the 1st century BC, or remaining Greek communities under the rule of the Indo-Parthians or Kushans in the 1st and 2nd century AD. Benjamin Rowland thinks that the Indo-Greeks, rather than the Indo-Scythians or the Kushans, may have been the models for the Bodhisattva statues of Gandhara Economy Very little is known about the economy of the Indo-Greeks, although it seems to have been rather vibrant. Coinage The abundance of their coins would tend to suggest large mining operations, particularly in the mountainous area of the Hindu-Kush, and an important monetary economy. The Indo-Greek did strike bilingual coins both in the Greek "round" standard and in the Indian "square" standard, suggesting that monetary circulation extended to all parts of society. The adoption of Indo-Greek monetary conventions by neighbouring kingdoms, such as the Kunindas to the east and the Satavahanas to the south, would also suggest that Indo-Greek coins were used extensively for cross-border trade. Tribute payments It would also seem that some of the coins emitted by the Indo-Greek kings, particularly those in the monolingual Attic standard, may have been used to pay some form of tribute to the Yuezhi tribes north of the Hindu-Kush. This is indicated by the coins finds of the Qunduz hoard in northern Afghanistan, which have yielded quantities of Indo-Greek coins in the Hellenistic standard (Greek weights, Greek language), although none of the kings represented in the hoard are known to have ruled so far north. Conversely, none of these coins have ever been found south of the Hindu-Kush. Trade with China The Indo-Greek kings in Southern Asia issued the first known cupro-nickel coins, with Euthydemus II, dating from 180 to 170 BC, and his younger brothers Pantaleon and Agathocles around 170 BC. As only China was able to produce cupro-nickel at that time, and as the alloy ratios are exclusively similar, it has been suggested that the metal was the result of exchanges between China and Bactria. An indirect testimony by the Chinese explorer Zhang Qian, who visited Bactria around 128 BC, suggests that intense trade with Southern China was going through northern India. Zhang Qian explains that he found Chinese products in the Bactrian markets, and that they were transiting through northwestern India,