The Number one Barbie had metal cylinders (see photo) in both legs with openings in her feet. These openings notice the metal cylinders so the 2 prong stand can fit  for doll posing.  (or holes), in the feet and legs, fit down on a pedestal stand with 2 prongs. These metal cylinders became costly to make for Mattel and seemed to be unnecessary for the doll as well. Therefore, Mattel decided to change the Barbie stand concept and went to a new style stand for the Number 2 Barbie doll. The Number 2 Barbie did not have the holes for these cylinders in her feet. This new stand, had no prongs. It came with a special shape wire added at the back of the disc for posing. Info: Use caution when purchasing a Number 1 Barbie doll stand. There are several places that make reproduction stands. The makers are upfront about the stands, though, in the wrong hands one could be taken advantage of.