seldom found (i.e., available on the public market) original danger or cautionary "no one permitted on tracks" porcelain enameled sign designed and fabricated by or for the chicago transit authority (cta). the small single-sided elevated railroad or "l" danger sign was removed from a signpost or wall in or around one of the chicago passenger stations. a former cta worker sold urban remains artifacts he collected from his years while working on station maintenance. the sign was "upgraded" with a cheaper molded plastic sign. the surface discoloration was caused from prolonged exposure to the elements. several signs in various configurations are posted along the tracks to warn individuals from coming into contact with the electrified third rail. only one available. measures 15 x 6 inches.