MLB Subway Sign with Field Dirt Oakland Athletics. This vintage-style Subway Sign is a must-have for any Oakland Athletics fan! Rather than showing the stops along a subway line, this unique sign details stops along the A's' history. Comes in a handsome frame, and measures 1" Thick. Features dirt from O.co Coliseum, authenticated by the MLB! Guaranteed authentic by Steiner Sports. Materials: Mica, Plexi, Glass, Dirt.