I suspect it's spurious, or at least, not a coin. I've never heard of a coin older than the 1300's with an AD date - the mediaeval Europeans were very slow to catch on to the whole "let's put the date on the coins" thing.
The eagle looks like the old Holy Roman Empire eagle
shown here, also used as the symbol of modern Germany.
Don't say "infinitely" when you mean "very"; otherwise, you'll have no word left when you want to talk about something really infinite. - C. S. Lewis