The Collaborative International Dictionary
Plaquette \Pla`quette"\, n. [F., dim. of plaque plate, plaque. See Plaque.] A small plaque, esp., in modern medal engraving, a small and delicate bas-relief, whether cast or struck from a die, or of form other than circular.
Wiktionary
n. 1 A small metal tablet decorated in bas-relief, usually with a design including figures. 2 (label en physics) The smallest closed loop, enclosing the region between four lattice sites, in http://en.wikipedia.org/wiki/lattice%20gauge%20theory.
Wikipedia
Plaquette is a French word meaning small plaque, especially small low relief sculptures in bronze or other materials. These were popular in the Italian Renaissance and later. They may be commemorative, but especially in the Renaissance and Mannerist periods were often made for purely decorative purposes, with often crowded scenes from religious, historical or mythological sources. Only one side is decorated, giving the main point of distinction with the artistic medal, where both sides are normally decorated. Most are rectangular or circular, but other shapes are found, as in the example illustrated. Typical sizes range from about two inches up to about seven across a side, or as the diameter, with the smaller end or middle of that range more common. They "typically fit within the hand", as Grove puts it. At the smaller end they overlap with medals, and at the larger they begin to be called plaques.
The form began in the 1440s in Italy, but spread across Europe in the next century, especially to France, Germany and the Low Countries. By about 1550 it had fallen from fashion in Italy, but French plaquettes were entering their best period, and there and in Germany they continued to be popular into the 17th century. The form continued to be made at a low level, with something of a revival from about 1850. They have always been closely related to the medal, and many awards today are in the form of plaquettes, but plaquettes were less restricted in their subject-matter than the medal, and allowed the artist more freedom.
Usage examples of "plaquette".
Roulette put down a plaquette with 800 written on it, positioning it fussily so it covered the number 25.