Eero Saarinen Tulip Stool ?

I have this set of four yellowish white metal tulip stools and I believe they are from 1950's-1970's. They are almost identicle to the Eero Saarinen style but the round cushion sits on top and the top of the stool has an edge that holds it in. The Saarinen stools don't have that edge. The bottom of each stool has a "KD" mark on the bottom. Help identify!