So curious! And to my eye quite a little jewel of a thing. I know nothing about it or where it came from, but it looks to me perhaps to be made of porcelain, as there is a bit of white showing though in a couple of spots near the mouth and the weight and feel seems right. And certainly it appears that an actual fish head was used as a mold, as the detail is quite realistic. I am not at all sure of the age, and have not found another out there like it. Perhaps there was once a stopper in order to use it as a perfume bottle (perhaps filled with a fishy scent!) or maybe just as a tiny vessel for one tiny perfect sprig.
2 3/16" t x 1 3/4" w x 3/4" d and in very good condition.