From another article:

“Most likely they were some form of religious or ritual object,” [Richard Parker, secretary of the Norton Disney History and Archaeology Group] said. “The Romans were a very superstitious lot, and generally required signs to allow them to make decisions in their daily lives.”

One indication supporting that idea is that the object was found near a small Roman mounted rider god figurine with “strong religious connections,” Parker said. The artifact was discovered in 1989 by metal detectorists, and the figurine is “often found on temple sites.”

and with the rise of Christianity, any such "magic" would have to be kept secret.

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"I drank WHAT?" (Socrates)