The owl is a give-away for an ancient coin from the city of Athens in ancient Greece. Rarely, however, is the owl depicted with wings spread. (This may, or may not, be your coin, Inadal. If not, use the Contact link to start an e-mail exchange.)
The coin in our main picture (to the left) is quite amazing. It is a large decadrachm weighing 41.5 grams. This particular coin sold for 130,000 Swiss francs, about $133000 US dollars, in a 2014 auction by Numismatica ARS Classica in London. CoinQuest thanks ARS Classica for use of their coin photo.
There is a good comparison of this coin with other ancients at Wikipedia.
With such strong value, there are sure to be replicas, reproductions, counterfeits, fakes of this coin. The image to the right shows one of them. Deal only with people you implicitly trust for coins like this.
Here is an interesting snippet from ARS Classica's auction catalog:
In fact, we now know the decadrachms of Athens and the Syracusan issues in the style of Kimon and Euainetos had legitimate and enduring roles in the monetary system, though never a commonplace one. The large silver coins of Northern Greece (principally octadrachms and dodecadrachms) were purely commercial coins, quite often struck for export. The decadrachms of Acragas, and possibly the 'Demareteion Master' decadrachms of Syracuse, may be exceptional in this regard, as the latter may have a yet-unrecognized commemorative purpose, and the former almost certainly commemorates a charioteer's victory at the 92nd Olympiad in 412 B.C.