File:LiveSteaming at GGLS PopSci Oct1951-3.jpg

Special four-rail track takes three gauges of locomotives - 2-1/2-inch gauge for 1/2-inch-to-the-foot scale; 3-1/2-inch gauge for 3/4-inch scale; and 4-3/4-inch gauge for the big one-inchers. From Popular Science, October 1951