A white queen chess piece, was seen in an evidence bag on the Mosaic Investigation wall in Mark's flashforward. It is also the title image of episode 1.02 "White to Play".
Following the encounter with D. Gibbons in the Divine Doll Company factory building in Pigeon, Utah, Mark and Demetri brought the piece to the FBI. ("White to Play")
D. Gibbons was later revealed to be Dyson Frost, who was famous for making a sacrifice with a white queen to win a championship game against Ian McKinnon. ("Queen Sacrifice")
After Mark gets the hint from Frost that Mark will be saved by "the lady he sees everyday", Mark cracks open the white queen chess piece, revealing a ring inside. ("Goodbye Yellow Brick Road")