Where Do I Go From Here With Gold Coin?

Well Syracuse Dekadrachms are usually 40g ish and fine silver, for this period. All are extremely rare and valuable and well cataloged, if you have one it is almost certainly a fake. Pictures of your coin would be most helpful. Front, Back and edge. Gold Dekadrachms are about 4 grams and are often cataloged as a number of Litra's 40,50,60, mainly during the 3rd cent BC, all fine gold. I am familiar with some Gold coins, but I am sure that people will not be able to help you all that well without pictures. If you do indeed have an ancient gold coin, then a fine auction house is where you would want to go. They will be able to authenticate it for you. A coin of that caliber should have proper provenance, where and when it was excavated and who the previous owners, and collection and or museum was. We need pictures!