Plastic mechanical computer from 1963: The Digi-Comp 1 [video]

Reproductions are still produced, see the wikipedia page.

I had a CARDIAC when I was young.

Really cool! Will we ever construct Babbage's Analytical Engine?

Wait til you see the DigiComp II! It has flip-flops driven by marbles and gravity. Truly astounding.

I had one! One of my favorite possessions in elementary school. It came with a nice booklet introducing the theory. Because I studied that booklet, I was probably the only brat in my 2nd grade who knew about number bases. I entertained myself by converting decimal numbers into binary.