This interesting and unusual plaque appears to be pate-sur-pate (a very expensive, labor-intensive method of building up thin layers of clay slip to form a raised image usually with great translucency on very fine porcleain). If this plaque was in bisque - instead of it being glazed - I would have to say it was jasperware but because of the high-gloss glaze, I do not know. Also, the weight of the plaque seems to indicate that it is not porcelain, but rather a ceramic base. Thus we can only say it is in pate-sur-pate style.
This glossily glazed plaque has an image of an upside down angel with a flag in his hand diving into the clouds seemingly from a large piece of lily-of-the-valley!
The ground color is 'prussian' blue - straight out of the old crayola box colors!
The plaque is in excellent condition and measures 8 3/4" x 6 1/2" x 1 1/4" deep.