It's a mystery.
Sometime after 1964, two rare early 19th century notebooks housed in a special collection at Girard College were taken. And no one knew they were missing.
But this year, they reappeared, and, thanks to the American Philosophical Society, they are back where they belong following a federal investigation.
The notebooks, from 1809 and 1811 and part of a set of four, were part of the Stephen Girard Collection and had been kept by H.J. Roberjot, Girard's clerk and right-hand man to document expenditures by Girard, the richest man in the United States at the time.
They gave an account of the daily life and generosity of Girard, the founder of Girard College, which he endowed in 1831 in his will. The school, which still operates as a five-day boarding school for grades one to 12, opened in 1848.
In 1964, the two notebooks were recorded on microfilm, according to federal officials. It wasn't until the early 2000s the school determined the volumes were missing.
"It is a mystery to us how they became separated from their partners," said Polly Mitchell, communications director, for the school.
The notebooks gave an insider's look at the generosity of Girard and his values, said Mitchell.
The college allows historians, students and alumni to see the artifacts in the "enormous" collection but not take them from the building. And, unless there was a reason to be examining the documents, there was no reason to suspect they were gone, said Mitchell.
Fast forward to July, when the American Philosophical Society was contacted by an out-of-town rare book dealer who had purchased the two volumes through a private sale, and would resell them for $17,500.
APS, the nation's oldest scholarly research institution, was founded by Ben Franklin in 1743 and is located at 105 South Fifth Street to promote "useful knowledge in the sciences and humanities." It has 13 million volumes in its collection.
It also houses microfilm of the Girard collection, which is not open to the public.
Charles Greifenstein, associate librarian, examined the notebooks when APS received them in early August. He immediately realized they belonged with the Girard College papers. A quick check of the microfilm found the exact notebooks, said Librarian Patrick Spero.
APS contacted Girard College and the FBI was brought in, said Spero.
"From there it took on a life of its own," he said.
Last week, the two volumes were returned to Girard College by the FBI and the U.S. Attorney's Office, which had been investigating their disappearance and reappearance.
The seller, who has not been identified, is not being prosecuted, federal officials said.
And Girard is just happy to have the historical documents back where they belong.