The Federal Bureau of Investigation announced Wednesday the return of approximately 120 historical artifacts to a museum on the northwest side of Chicago.

FBI officials say those artifacts, which are valued to be worth between $4 million and $5 million, were removed from the Polish Museum of America sometime in the 1980s.

Maria Ciesla, the president of the Polish Museum of America, said a local coin and antique dealer called to tell her he had purchased documents he later traced back to the museum.

“I couldn’t catch my breath because this was a phone call we had dreamed about getting,” Ciesla said. “This was the first tangible proof that this was not a rumor, that these were out there, that these documents and artifacts were out there.”

Ciesla said nobody currently on the museum’s staff had worked there when the artifacts disappeared, so the only information they had was “rumor and innuendo.”

Harlan Berk, the coin and antique dealer who contacted Ciesla, said the individuals trying to sell the artifacts said they had discovered them in the basement of a house they were renting.

The FBI said that house was owned by the mother of a former curator at the museum.

Berk said he continued buying artifacts from the individuals over a two month period. He said when they told him they were planning on auctioning some pieces off, the museum contacted the FBI in October 2011.

After an investigation, the FBI found several other artifacts in the basement of the house. However, FBI officials said they could not establish the date the artifacts disappeared or the person responsible for removing them. They say, as a result, no criminal charges would be filed. FBI officials also said the statute of limitations had run out.

Ciesla said all the artifacts will be returned to the museum to be put on display sometime within the next two years. Berk said he’s just happy to have helped.

“We’re absolutely thrilled,” Berk said. “Anytime we can do something good, we’re very, very pleased to do it.”

Artifacts included letters to and from historical figure like Thomas Jefferson, Abraham Lincoln, Napoleon Bonaparte and American Revolution hero Thaddeus Kosciuszko. The artifacts also include Nazi propaganda from World War II.