A charming small whimsy, and an unusual one as far as I've ever seen, shaped like a bottle--I am thinking perhaps made as a toy rattle to emulate a baby bottle, and there's even some darkening to the bottom as if heated over a stove! Skillfully carved with a lovely intricacy to the neck of the bottle and "walls" at either end of the cage, which houses a very roundly caved ball. It will stand on its own on from the opening end but takes a flat surface and a little balancing.
4 1/16" l x 13/16" wide and deep. Very good condition, Nice dry wood patina, I'd guess 1920s-40s.