In the late 1960's, the Italian manufacturer Artemide, best known for their groovy light fixtures, produced this stackable kid's stool by Stacy Dukes. It's called the Efebino, though there was also a slightly wider, 2x taller version called the Efebo, too. They're made of ABS plastic, once The Material Of The Future.
They turn up now and then for about $75-100/each at places where these kinds of things turn up. [Treadway Gallery sold one at auction last year for $225, paired with the similar but unrelated Casalino chair.]
Near as I can tell, Stacy Dukes later built a prolific practice in Orange County doing corporate interior work. The project backlog is so great, in fact, they haven't had time to update their website since 1999
image via freakando, who apparently organized an exhibition in Bologna in 2005, "A misura di bambino. 100 anni di mobili per l’infanzia in Italia." looks interesting. [freakando]
Stacy Dukes Design [stacydukesdesign.com]