Decagram? Real? How To Tell.

Syracusan dekadrachms are some of the most famous and most often faked ancient coins.
Why?
The genuine examples are all extremely valuable.

Amongst other things, some of the unscrupulous will go to an extraordinary amount of effort to make a fake as close to genuine as possible.
The best fakes are often of correct weight, and in good silver.

I have three rather obvious fakes of this coin,
one close to correct weight, silver plated. It betrays itself with the remains of circumferential casting join.

The advice of John1 would be a good start in the investigation of the coin pictured. Would be of great advantage if the edge of the coin is also pictured.

to the Community!

to the community

As already been stated this is one of the most copied ancient coin. Genuine examples sell for more the $100K depending on condition. It very difficult to tell if it's genuine from just a picture. Your best bet it to take it to a museum that has and ancient coin collection for evaluation. Or to send it off to David Sear and have him check it out. He charges a fee for the service.

https://www.davidrsear.com/certification.html