The items were illegally shipped from a father in Italy to his son in Berwyn over a 20 year period of time. The valuables were discovered after the Berwyn resident died two years ago.
The items are worth millions. Most are from the Renaissance period and all come from the Bari region in southern Italy.
A manuscript written in 1395; terra cotta figurines that date back to 500-900 B.C; and something a bit more recent, a hand written document by Benito Mussolini. This is just a sample of the 3,000 religious artifacts, books and antiquities found two years ago in an unremarkable Berwyn brick bungalow.
"This is definitely the most unusual thing I've ever encountered. It's absolutely amazing. It is like walking into the DaVinci Code," said Chief William Kushner, Berwyn police.
Berwyn Police Chief William Kushner was called to a home in Berwyn two years ago after the owner John Sisto died. Sisto's sons alerted police after discovering their father's hidden treasures. The house was under constant police protection while the FBI began a long investigation.
"To date we have determined that approximately 1,600 items were taken illegally from various locations in Italy. They were shipped to this country between 1960 and1982," said Ross Rice, FBI spokesman.
The FBI says the items were shipped to Sisto from his Italian father for the purpose of having the younger Sisto sell them for profit in the United States.
The FBI says the value of the stolen items was estimated at between $5 to $10 million.
It's all comes as a big surprise to John Sisto's Berwyn neighbors.
"I'm pretty shocked...that it would be across the street and nobody ever knew about it," said Gloria Saunders, neighbor.
"I think he collected it not knowing how much it was worth because…he was not flashy, he didn't look like he spent money," said Ruel Quinones, neighbor.
That is because John Sisto never sold the items.
"Our theory is based on our investigation is he was more interested in the historic value of the items than monetary," said Rice.
And the FBI says the items would be difficult to sell in an open market because most are archival documents. Besides letters from popes and kings, the most expensive in this collection is a doctoral degree from 1662.
"It's written in parchment and it details the person who got it and what he did. I think it's quite a spectacular piece," said Bonnie Magness-Gardiner, FBI art crime team.
The 1600 items that were taken illegally will be returned to Italy this week. While several Italian and American laws were broken. No one has been charged criminally with the investigation since the two men involved are now dead.
The FBI's art crimes team says art and artifacts theft is world's third biggest crime drugs and arms trading.