Attorneys from Pepper Hamilton are aiding a Delaware author in his bid to force the FBI to release records of the agency’s investigation into the theft of crown jewels belonging to the House of Hesse, a German royal family, by U.S. soldiers at the end of World War II.

The Pepper Hamilton lawyers representing the author, William McMichael, said in a federal court filing on Tuesday that the FBI has improperly withheld more than 7,000 pages of documents potentially related to the heist, which resulted in the court martial and conviction of three U.S. Army officers in 1946.