405 Bc. Greek Coin 3.68g Silver

I for one would need more info, as well as complete pictures of the coin in hand (without overlays), to venture any informed opinion.

You state you "weighed it and measured it." Does the 3.68 gram weight you mention in your post's title refer to your boss' grandfather's coin, or the one on the auction site? Are the weights and measurements identical? If not, how far off are they? Are you assuming your boss' coin is an ancient drachm?

For that matter, what issue do you think it matches? Is that a coin of Katane (Catana), Sicily (w/Silenos obv) you provide above?

Based on what little you show of your boss' coin, the silver and fabric do not look like a match for an ancient issue of Katane. But, without a complete picture, I couldn't say for sure.

I also see nothing at all on the reverse (the second to last picture seems to show an entirely blank surface), but perhaps with a better image there might be something. Your last image is confusing too - I see the auction coin's features from the overlay, but it's unclear to me what you're seeing as an alignment to your boss' coin.

Perhaps your speculation/attribution is correct, but personally I would need more info to judge.

Thank you both for the responses.I will try to take better pictures, but with the fact it's so worn, I might not be able to. With the naked eye, and in the pictures, you can see some features that appear to match this coin. So far this coin is the closest I can find. The overlays, as I slid the lever back and forth, just helped me orient the coin and to help confirm I was seeing what I was seeing. I will try again this morning to provide better images and reply as soon as I get them. Thank you