What a curiosity! I was pretty excited to find this little antique French reversal drawing, which I believe dates to the 1840s or so, when optical illusions because a big thing in France (check out the phénakisticopes published by Joseph Plateau)  and reversal portraits were circulated. (I'm including one by Daumier in the photos)

This one has a very contemporary feel to me, perhaps in part because the human face keeps reminding me of the late great David Foster Wallace!  I don't think the horse side of the portrait is especially convincing, which honestly makes me love it more--a strange hybrid thing, neither this or that. Nicely executed in ink wash/watercolor and mounted to a backing sheet the perfect shade of blue, framed in two slightly imperfect black ink squares and captioned with handwritten text on either side asking 'Lequel est mon portrait?"

Drawing itself paper size is 3"x3". Sheet size is 5 1/8" x 7 3/8". Good antique condition, with some darkening to the blue paper along the left side and small stains here and there, minor.