As others have told you elsewhere, Tranquillina imperial antoninianii are five-figure coins. Five figure coins attract individuals who can make very good replicas. I am still a little confused about what exactly "found" means. Did you dig it up out of the ground in Italy? Find it on the street? Find it in a Coinstar?
If you are absolutely convinced that it's real, send it in for certification. What's a $20 fee for a $15,000 coin?
New Sale! Inexpensive classic Greek silver, over 2,400 years old!http://goccf.com/t/323297