FREDERICK, Md. (WDVM) — The Monocacy Battlefield Foundation (MBF) donated a piece of Civil War memorabilia to the National Park Service (NPS) on Monday. The memento — which, according to the NPS, is a “rare” piece of Civil War history — is the I.D. tag of a soldier who fought in the Battle of Monocacy on July 9, 1864.

Until the introduction of standardized “dog tags” provided by the United States military, soldiers had to find ways to ensure their remains could be identified if they were killed in battle, the NPS wrote in a press release about the donation. For this reason, these older I.D. tags were all unique and there’s no record of how many exist.

“It is amazing that after 157 years, this ID disk is returning to the battlefield,” said Andrew Banasik, superintendent of Monocacy National Battlefield. “This small piece of metal is a tangible reminder of the price paid by so many to save Washington.”

The I.D. tag belonged to Samuel M. Weigel, a private in the 138th Pennsylvania Infantry, who was injured during the Battle of Monocacy but survived and lived until 1922. The tag will be placed in the National Park Service’s museum.