The Saint Louis Museum of Art has three of these mysterious bronze discs, which they suggest are shield bosses or ornaments for armor. I'm not sure why they think this; they don't say, and so far as I can tell these were all discovered in the nineteenth century. Anyway they all come from Italy and are dated to the Orientalizing period, c. 700 to 600 BC. Some are Etruscan, but others are from other areas and are designated Italic.
Very cool objects.
Since I liked these so much I searched for more but didn't have much luck; I found this one on Pinterest, apparently from an old sale at Christie's in New York. So these are not such rare items. But beyond these four all the Etruscan Bronze Discs or Etruscan Shield Bosses i have found have abstract designs, like this one in the Boston MFA collection. Not nearly as much fun as these.