Early 19th century Japanese plique a jour button-pendant. This is not the same as painted glass, but rather layer after layer of glass enamel is fired over a copper base, in clear and different colors each time, each layer taking its time. Earlier the wire cloisons would be fired over the clear enamel base before the colored layers are added, layer by layer until the desired translucence is achieved.
This joyous Japanese piece is a generous size button, about 4.5cm, to be worn as a pendant. It is uncommon to find a plique a jour enamel piece in this size. Its colors are actually lighter and almost pastel in daylight.
(via Plique A Jour Pendant, Japanese Flower)