Wood 6-bit adder
Heh, in the days when I was doing network subnetting a lot more, that would have been, if nothing else, novel to have sitting on the desk.
Heck, I think the inner-geek in me would still have one sitting on the desk just to confuse people.
My kid has a cool marble rolling toy called Quadrilla, and I’ve been wondering for months if I could get it to compute. After checking out this picture, I bet I can!