I am by no means an expert on this coin having only seen pictures of them. That being said, it is a highly sought-after coin and there are tons of fakes out there. I don't have a warm fuzzy about yours being real. Can you take a picture of the edge too? It looks like there is a seam.
There are fakes of practically any coin ever produced. Yours is obviously not the one in that auction. If you would like some opinions, you need in-focus pictures of the coin you have along with the weight and diameter in mm. Please post the pictures full size.
The bubbly surface and what looks like a casting seam cast great doubt on this. Where did you get it and what did you pay. If it seems too good to be true, that's probably the case.
19.95 US + free shipping + bonus: a nice casting seam... https://www.ebay.ca/itm/Greece-Ital...116148?hash=item3fb7a705b4:g:mFkAAOSwL-1cQyBa
I've seen replicas sell for $20 to $100 or more, depending on who made them, what they're made of (silver or not), and how high quality they are. Yours doesn't look like a high quality one, and I have some doubts it's silver.
Weight is the easiest way to tell. The Triton T-2 is probably good enough for your needs: https://www.oldwillknottscales.com/my-weigh-triton-t2-120.html You can do a specific gravity test, too, but you'd still need to know the weight to calculate the s.g.
The genuine example shown in the Numismatica Genevensis sale is a good standard. I do not have the numbers in front of me, but, basically, every known example of this coin is accounted for. Every sale comes with a long line of provenance (previous owners). More to the point, Numismatica Genevensis is a member of the IAPN (International Association of Professional Numismatists). And you can read about their sales in Coins Weekly (https://coinsweekly.com/numismatica-genevensis-sa-ch-genf-4/) and their auction catalogs are for sale on the aftermarket (https://www.abebooks.com/book-search/title/numismatica-genevensis-sa/). So, you found a good comparison to judge against. Against that, you have a coin that you say was given free as a gift that you "... didn't pay nothing for..." As for the "pennies" not all of them weigh the same. It matters what year they were struck; and 15 of the most modern issues come to 37.5 grams (2.5 grams each). So, with this coin known at 43.17 grams, you are "two pennies short of a decadrachm." As you apparently do not collect coins, if we may ask, what is your interest in ancient history that some close personal friend thought to give you this nice copy of a piece of classical Syracuse?
There are a hundred different fakes of this popular coin. While a casting seam is a bad sign, the lack of one is no reassurance since there are original modern dies that produce struck replicas that will fool people who know nothing about the real coins. This one is the Antiquanova in tin. They also make one in silver but that one is more expensive because of the bullion value. My favorite replica was made in 1898 as an advertising giveaway for the Stearns Bicycle Co. in Syracuse, NY. Obviously it won't fool people into believing it is ancient but these are collectible in their own right.