You are probably referring to the Eldorado building with the bridge. This error was created by the GDC mint who put the walkway to the casinos parking garage on the side of the building which is along the railroad tracks. The walkway had to go and was taken off the strike after only a few of the strikes were made with the "G" mint. The is a second highly saught after strike with the bridge obverse that has the current SMALLER LOGO which is used by the "G" mint. Hope this helps. Jack