Not really fair on the OP as his post started with: "I bought an auction of misc. stuff and inside I found a coin which is most definitely at a minimum a replica of an athena/owl tetradrachm. My question to the crowd, is can you provide me any insight on the key indicators or replica vs. original?" This is a good question from someone with no experience and I hope he feels that he has posted in the right place ... The rest of the thread has shown that as far as "key indicators" this is a difficult question to answer as there is at least healthy debate on this front. I hope that any determinations will be posted here so "new posters" (like me) can learn.
I think that this one from catawiki is possibly authentic and was the mother for the Beirut forgeries! There are scratches on the left side on the reverse copied the mother https://auktion.catawiki.de/kavels/...e-der-stadt-athen-geschlagen-in-449-413-v-chr @ Jay GT4 You have strange holes (some are very circular) in the letters alpha, omicron and epsilon, I do not like the tonig or dirt and the scratches. How does the edge looks like?