Grand Ole Opry stars Marty Stuart and Connie Smith gave a sweetheart gift to the Country Music Hall of Fame and Museum on Wednesday, the day before Valentine's Day.

The couple, who are married, donated bluegrass great Lester Flatt's 1950 Martin D-28 guitar along with several other items from their personal collections of music artifacts and memorabilia. The instrument, which some have called "the holy grail of bluegrass guitars," was used on most of Flatt & Scruggs' classic recordings and live performances. The Hall of Fame duo are perhaps best known for their tunes "Foggy Mountain Breakdown" and "The Ballad of Jed Clampett," from the 1960s TV show "The Beverly Hillbillies."

Flatt bought the Martin for $115 at a Charleston, West Virginia pawn shop in 1956. In the 1970s he loaned it to Stuart, a native of Philadelphia, Mississippi, who was then a prodigy in his band. Stuart fell in love with the guitar and often played it until Flatt retired and disbanded his group.

Stuart thought he'd never see it again, but after Flatt's death in 1979 he was able to buy it from Flatt's daughter, Brenda, and has had it ever since. "It's possibly one of the greatest rhythm instruments ever made," said Stuart, an avid collector.

Stuart and Smith also donated some of their own stage costumes and instruments to the Hall of Fame as well as items once belonging to music icons Johnny Cash and Hank Williams.