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