LONDON — A chess piece purchased for a few pounds in 1964 has been identified as one of the missing 900-year-old Lewis Chessmen. Sotheby’s auction house said Monday that the piece could bring in between $670,000 and $1.26 million at an auction July 2. The Lewis Chessmen are intricate, expressive chess pieces in the form of Norse warriors, carved from walrus ivory in the 12th century. The piece is the first of the five missing chessmen to be identified from a hoard of 93 that was discovered in 1831.