Here is a vintage magazine advertisement for a Flexible Flyer sled that was manufactured by the S. L. Allen & Co., in Philadelphia. The ad states that this sled is self-steering, you manage it without your feet on the steering bar, and it goes faster than any other sled. The ad is from the December 1893 issue of St. Nicholas magazine. Here is a black and white version of the sled from the ad. Click on images to enlarge.