Not e-bay, but in an upcoming auction from an established dealer. This Emesa mint denarius of Julia Domna is very hard to come by and I'm interested in it. But its porous and flaking surfaces make me a little cautious about casting. Any thoughts? Seller's photos.
Looks authentic to me, just patchy toning. In fact, it's a die duplicate to another coin on acsearch. Search for domna and the RIC number and you'll find it.
Looks good to me. Here's a comparison piece, FWIW: Same mint; obviously different dies. Given the appearance of the surfaces you can check it for evidence of casting, but I'm guessing it will be okay. If you have serious doubts, leave the door open by letting the house know that you will want to return it if it doesn't check out.
Not at all sure where you get the idea that an age-eroded surface like that seen on this coin is the result of it being a modern cast - but no, that is a completely believable piece which has been left very close to the state in which it was discovered and has not (as is all too common) been cleaned to within an inch of its life (and removal of any evidence of authenticity) by someone enamoured of all things "shiny". It might be possible that a very skilled forger could have degraded a struck or pressed modern copy to give it a surface similar to that acquired over a couple millennia-worth of "diagenesis", but someone with those skills could have employed them far more profitably faking other types.
These are hard to find well centered, well struck and with pleasing surfaces. Two out of three is not bad. Mine are worse.