Thomas Gavin, 78, of Pottstown, was sentenced Tuesday for the theft of a rare antique rifle during a visit to the Valley Forge State Park Museum in 1971. Gavin kept the Christian Oerter flintlock rifle, a relic of the American Revolution, in his barn in Pottstown for decades before selling it to a dealer who recognized its significance. Gavin will spend one day in prison and has been ordered to pay nearly $50,000 in fines and restitution. The rifle was returned to its owners and is now displayed at the Museum of the American Revolution in Philadelphia.