Replica?

Cast fake.
Keep it. I like it anyway.
I have about 100 fake ancient coins for study purposes, to educate myself in how to spot fakes.

There are two easy telltale indicators for this coin.

First, the casting has left "bubbles" on the surface. While a combination of corrosion and improper cleaning can leave an ancient bronze coin covered in pits and craters, there is no natural process that can cause anti-pits to form on a coin. That's a sure sign that it's a cheap cast.

Second, is the type depicted. This is a very scarce type of the early emperor Caligula. Worth thousands or tens of thousands of dollars, if genuine. Wildwinds examples. They generally aren't just sitting around unidentified someplace. I always assume that a super-rare, highly sought after coin type like this is a replica, until I can prove otherwise.

In a few hundred years it will be a piece of history......but hey, if you like it, keep it and enjoy it, why not. Collecting stuff is about the enjoyment YOU get from it. I am about to start collecting historical medallions from the 18th 19th C, they are so beautiful and I have been wanting to start a nice collection for a while....ebay has some v nice ones at the moment, especially a siege of Bastille one , but its pricey.