The 3-cent Children's Stamp was issued on December 15, 1956, in Washington, DC. It was issued to promote friendship among the children of the world. The design features a group of children "looking toward the right in the pleasurable prospect of attaining the radiant Key of Friendship with which to unlock the doors to peace." (source: Arago)
This is a Velvetone Maximum card produced and distributed by Edwin P. Haworth. Note the instructions at the bottom of the back: Even if bearing a stamp on other side, this card MUST NOT be mailed unless bearing two cents postage on this side."
This is a post for Sunday Stamps at Viridian's Postcard Blog