Wiktionary
plaquet
n. (context archaic English) A strong metal plate used to reinforce the lower part of the breastplate in a suit of plate armor. A placard.
Usage examples of "plaquet".
It's in a big iron-cornered box, locked in a stone vault behind an iron-ribbed door and Monsieur Plaquet has one key to the vault and I have the other.
He knew that a heavy fall of snow would never let him reach Caen and back in a day, but nor did he have any intention of going to Caen, for Monsieur Plaquet did not exist, nor was there any great iron-bound chest in a stone vault on the Rue Deauville.
The only light, once the door closed behind him, seeped through the skylight, a tracery of mica plaquets now opaqued by layers of steam and soot.