I believe this is likely German and dates to the 1920s or so, and in the ensuing 100 years has lost a fair amount of its top layer veneer of sorts, which would have included labels for the individual molars. I love it precisely for its decay, amazing surface, and terrific object hood, recognizable as a jaw but also looking a bit like a model of earth strata, and then perhaps best of all what look like tiny faces on many of the teeth, eyes peering out as if pleading for extraction (and making me feel quite empathetic toward them!)
There's a fair amount of color on it still, and apart from loss to the top layer, there are no significant chips or cracks. It seems a bit more like ceramic than plaster (and is quite heavy), but I am not 100% sure. Mounted to a black painted solid wood board, original to it, and very sturdily attached.
13" wide x 7 7/8" tall x 7/8" deep.