Authentic or counterfeit: Thrace Thasos AR tetradrachm?

Hello all,
I purchased this coin on ebay under the listing "GREECE TETRADRACHMA - THASOS silver coin 15.33 gramm E2".
It is slightly convex, with the obverse side "popping out".
My concerns are with the markings on the reverse side.  The letters and symbols do not match with certified examples such as:

http://www.apmex.com/product/83336/thrace-thasos-ar-tetradrachm-2nd-1st-cbc-vg-ngc

I have taken it to two local coin dealers to get a few opinions but they primarily deal with US coinage.  They were able to verify is that it is likely silver, and it does weigh 15.3 grams.
I must also mention that I did not drill the hole in the coin.

I now realize I should have posted my previous post under "Coin identifications and valuations" (I am a first time poster).  Can I move the post to its proper place?
Thanks

its not more worth than material with the hole so i hope you didnt pay too much

I definitely got ripped off and am embarrassed to say how much I paid for it.  Because of how much I paid I am trying to determine if it is even authentic. If it is not authentic I can file a dispute on paypal and send it back for a refund.  

file for a refund.

More bad news: It has been more than 90 days so the item cannot be returned.  I had that sterling mount put through the hole once I realized it was worth about as much as a silver half dollar. More useful as a necklace than a coin.

At least I have a gift lined up for my girl!
Thanks for all your help.

Citeer: klangdonI now realize I should have posted my previous post under "Coin identifications and valuations" (I am a first time poster).  Can I move the post to its proper place?
Thanks

I moved it for you. Welcome to the site also.