For me, as a great lover of antique school slates, this is as good as it gets. I have seen (and bought and sold) exactly one other slate with narrow, rounded frame like this in my years of looking for them--a shape which I find exceptionally graceful (and the thinness of which makes the slates survival seem all the more improbable), and which makes me think of bentwood  boxes, too. And this one has an iron mend along the bottom edge of both sides to boot. And I do not think I am hallucinating in seeing the year 1851 carved into the slate just above the mend on one side, oriented in the opposite direction.  Special and to my eye quite sublime.

 14 1/4" x 10 1/8". Good antique condition. One edge of slate visible, all to the good in my opinion, and it will shift just a bit in the frame when one rotates it. General surface wear and age to slate itself, with a light, fine hairline surface crack on one side, minor and really only noticeable when looking for it.