As I posted elsewhere on the topic...
Finding any Roman coin is rare in Poland, since Poland is well beyond the boundary of Roman territory. Finding Roman coins in a proper archaeological context in Germany is scarce enough, and Poland is even further out into the darkness (from the Roman point of view). I'd imagine this treasure-hunting group in Poland would be mostly used to finding relics from WWI or WWII.
"Denar" is, of course, the Polish name for the coins, which for some reason has not properly translated. In English, we normally call them a "denarius".
I'd like to see the "Visigothic denarius". The Visigoths didn't arrive on the Roman borders until around AD 300, long after Antoninus Pius denarii would have vanished from circulation, and generally lived far to the south of Poland. So it probably is "barbaric imitative", but not Visigothic.
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