Reading a struck coin
An ancient coin was struck between two engraved dies, with a hammer. That act leaves recognisable traces, and they are the first thing you look for under a lens.
How coins were struck
The flan, heated, was placed on the obverse die set into an anvil. The reverse die, held in the hand, took a blow from the hammer. The metal then flows outward and fills the hollows of the engraving.
Everything follows from that. The relief is crisp, the letters have sharp edges, the metal sometimes curls back at the rim where it has spread beyond. The edge is not smooth: it carries the folds of crushed metal, often with a slight lip on one side.
What to look at
Centring first: few ancient coins are perfectly centred, and a slight shift is a good sign rather than a fault. Then die breaks, those small fractures in the die that leave a raised lump on the coin, always in the same place on every piece struck from that die.
Double strikes show as doubled letters: the die bounced. Overstrikes, where an earlier coin can be made out beneath the new one, are common in periods when metal was short.
What separates a struck coin from a cast
A flan poured into a mould does not behave like a struck flan. The angles are soft, the letters rounded instead of sharp, and the surface often carries minute bubbles where air was trapped. The edge sometimes shows the seam of the mould.
This is why examination under a binocular lens comes before everything else: it does not tell you whether the attribution is right, but it tells you how the object was made.