MLB Subway Sign with Field Dirt San Francisco Giants. This vintage-style Subway Sign is a must-have for any San Francisco Giants fan! Rather than showing the stops along a subway line, this unique sign details stops along the Giants' history. Comes in a handsome frame, and measures 1" Thick. Features dirt from AT&T Park, authenticated by the MLB! Guaranteed authentic by Steiner Sports. Materials: Mica, Plexi, Glass, Dirt.