How To ID Casting

This recent thread has an excellent example. Look at the third picture, of the edge. There's a line right through the middle of it, especially visible on the left side of the picture.

The seam is caused by metal leaking out of the gap between the two moulds used to make the fake coin from. Genuine coins were (almost) always struck, not cast, and nothing in this primitive minting process touched the edges of the coins. So genuine ancient coins should not have such a seam.

Fake-makers know that a casting seam is surefire evidence of a fake coin, so they (or secondary on-sellers) may try to file or grind off this seam from their more blatant cast jobs. So look for file marks on the edge of a coin, too.

The other thing to watch for on casts is the bubbly surface. Now here, I must be cautions. A pitted, rough-looking surface may be a sign of casting, but may also be perfectly explainable on a genuine coin as corrosion. But a distinctive sign on cast coins are "bubbles", extraneous dots and points on the coin's surface that are raised up, rather than pits that are sunk down into a coin. Such a feature is caused by a bubble of air getting in between the mould and the seed coin which the mould was made from, creating a hole in the mould. So if you find dots, spots and other raised features that "shouldn't be there", you've most likely got yourself a cast fake.

On the cast fake linked to above, look in the centre of the obverse, on Arethusa's cheek - there's a "beauty spot" there, a raised dimple. Ancient Greek artists were idealists who preferred their artwork to be defect-free, so we know for sure that that particular dimple cannot have been on the original die a decadrachm was struck from. The only explanation is it's from a second "die", in this case a casting mould. Once you know what to look for, you can see similar dimples all over the surface of this coin.