Theories as to what's happened with this penny?

[RChris]

Another acid bath victim perhaps? Any other theories? It weighs 9.1g

[Rob]

The visible lettering is too crude and close to the rim IMO. It looks more like an abused attempt at a cast copy to me. Any attempts at acid cleaning will thin the letters and reduce dimensions on all 3 axes if there is total immersion. The weight of a cast would obviously depend on the amount of metal poured into the mould, so I think not relevant in this instance.