I found this card at the hobby store near the Railroad Museum of Pennsylvania in Strasburg. It is a credit card-sized plastic card that helps you quickly determine if an item is of the proper scale. The company that made them closed its doors at the end of 2012, but you might be able to find these in hobby stores. This particular card is for measuring S-scale figures. It shows a typical 6-foot tall male and a 5'6" tall female. However, since it has a scale ruler along two of its sides, it is also useful for measuring other things, such as automobiles, detailing parts, and maybe even structures.