In the field of classical studies, in particular, where the quantity of sources is very restricted, coins constitute a major body of historical, economic and artistic material and evidence. The surviving coins by far outnumber other groups of sources such as ceramics and inscriptions, and, contrary to most other classical remains, they automatically mirror the public sphere, as by definition their value and acceptance must be guaranteed by the state. So coins – both in themselves and in the context of hoards – are not only sources for economic history or just a medium for art-work, but they can also give extensive information about – official – religion and cult, political thought, ideology and autonomous artistic features such as portraiture as well as monetary policy. Nevertheless, the numismatic material is still far from being incorporated or understood, and is not well exploited in classical studies overall. In Greek numismatics, with its countless coin-striking authorities – the poleis, tribes and dynasts – the material is still undergoing the process of collecting and classification. In many cases, the very existence of a polis is only known from its coins.