Handprint on Declaration of Independence remains a mystery

The Declaration of Independence is key to the nation's founding, but the document itself hasn't always been handled with the delicacy it deserves.

One such consequence is a handprint in the lower left-hand corner that still remains a mystery.

According to the U.S. National Archives website, "The origins and circumstances of the handprint are not known. The document was handled, rolled, and traveled about and exhibited extensively in its early life."

A conservator with the agency told CNN that one theory places the blame on a worker at a Philadelphia frame shop who may have had printer's ink on his hand during a re-framing of the document in 1888.

The same expert had previously revealed to the PBS program NOVA that the staff at the Archives did discuss the possibility of removing the smudge but ultimately decided against it.

Among other issues, cleaning the document could damage the parchment.