One of the things I really love about old wooden stools is that typically they've been put to hard use, and they show it! This very cute small slatted one has a few screws augmenting the nice old nails joining slats to sides, and newer reinforcements screwed to either side to sturdy it up. While these might be eyesores to purists, I love seeing these investments in preserving the utility and longevity of this trusty old thing! 

I'd think late 19th century and believe the wood is pine. 12" wide x 7 1/2" deep x 7" tall. A little splitting to the wood around the nails but the slats are firmly attaching and it is quite sturdy still.