It has a fine walnut stock, a blue finish and a very simple inscription that reads “Albee to Lawton.” But this 19th-century rifle has become the most expensive single firearm ever sold at auction according to the Rock Island Auction Company, which recently sent the historic piece to a new destiny with an undisclosed buyer. The price: $1,265,000. “Other guns have sold higher as a pair, but no other single firearm surpasses this new world record. It was an honor to be entrusted with an American treasure,” said Kevin Hogan, president of the Illinois-based company. The rifle itself was a...