I was chatting with Dorothy King, PhDiva last week about the "Leutwitz [aka Cleveland] Apollo" and the question of it being an original Greek bronze came up (Dr King has been suggesting that it might be a Roman copy, and - not being a Greek statue buff - I was curious to learn why). This point was made and she said I could quote her:
the main argument for it being an original would have to be it being found in an archaeological context. Even when it is, for example Praxiteles' Hermes found at Olympia, there is debate about whether the Hermes was an original (probably) or a Roman copy (doubtful). There are so few surviving ancient Greek bronzes, and so much variety in the techniques used, that the prime argument in terms of date would be the context, which here is missing.That is Cleveland's problem in a nutshell, they've bought a contextless geegaw and can "infer" and speculate on "style" and "iconography" all they want, but that is not the hard information true scholarship needs.