Manassas National Battlefield Park kicked off the week marking the 150th anniversary of the Civil War’s first major battle Monday by unveiling an exhibit featuring a belt buckle worn on the field by famed Confederate general Stonewall Jackson and a shotgun carried by southern partisan leader Col. John Singleton Mosby.

A West Virginia couple lent both items to the park after acquiring them in an auction two years ago without realizing their full importance.

Thursday marks the anniversary of the 1861 battle known in the South as First Manassas and in the North as First Bull Run. It was the first major engagement between armies in the Civil War, and the one in which Gen. Thomas Jackson acquired his nickname because he and his troops held their ground “like a stone wall” under Union attack.

North and South fought a second major battle on the same site the next year.

A Mexican officer originally owned Jackson’s belt buckle, which is illustrated with the Mexican national symbol of an eagle devouring a serpent. Jackson brought it home as a trophy from the Mexican War, in which he served.

The shotgun is signed by Mosby and labeled, “my first cavalry gun.” Mosby, nicknamed the “Gray Ghost of the Confederacy” because he was so elusive, led rangers who staged raids behind Union lines in Northern Virginia.

“Having these items really helps people connect to history,” park Superintendent Ed Clark said at a brief ceremony inaugurating the exhibit at the park’s Visitors Center. “The first time I held that belt buckle, it gave me goose bumps. You feel like you’re holding history.”

Greg and Patti Paxton of Charles Town, W.Va., had only an inkling of the two items’ historic value when they bought them in April 2009. They bid for them successfully at an auction of the estate of the late Bob Daly, who owned the Powder Horn Gun Shop in Middleburg, Va.

“All we knew when we bought it was it had something to do with Stonewall Jackson,” Patti Paxton said of the buckle. “We had no idea. We’re green to this, even to today.”

The Paxtons, who own an auto repair shop in Winchester, Va., declined to say what they paid. The buckle and shotgun were authenticated with the help of a local historian and experts at the University of Virginia and elsewhere.

The exhibit will be on display until the end of the year.

Park Curator Jim Burgess said it felt like “Christmas in July” to have the two items for the anniversary.

A series of events is planned to commemorate the battle. They include a ceremony Thursday where Gov. Bob McDonnell will speak, a parade of Civil War reenactors Friday, and a reenactment of the battle Saturday and Sunday.