These are exceedingly rare tetradrachm (16 to 19 grams) with two eagles gloating over a killed hare, a (usually female) driven fast quadriga and an 8-legged crab. The example in our picture comes from Gemini Auctions where it sold for (are you ready?) $75000 US dollars during a 2011 auction.
Obviously, you must pay a great deal of attention to this coin if you have one. There are larger denominations (e.g., dekadrachm, 40 grams), different orientations (right, left) of the eagles and quadriga, and plenty of fakes. Be sure to enlist the help of reliable professionals with this coin.
Each coin stands on its own merits. Auction prices range from $5000 to $100000 for genuine coins.
Even some fakes are valuable, sometimes garnering decent money. The counterfeits in the picture to the right are worth money, about $500 for the nice one, about $2 for the not-so-nice one.
CoinQuest thanks Gemini for use of the photo of the genuine tetradrachm. It's a beauty!