Here’s the photo we can’t use, because it’s from LiveScience:
http://www.archaeology.org/images/News/1606/Scotland-silver-hoard.jpg
Looks like a hoard of money clips.
Since there's no scale in that photo,it's hard to estimate size. Those two hemispheric "domes" look a little small for the purpose -- but they look like "targe" (shield) bosses -- made to surround-- and decorate -- the base of a central spike...
So I guess the Roman Empire existed to the 5th century? I guess a movie was wrong?