This is a vintage French ceramic majolica oyster plate,  in turquoise color, made by Gien, circa 1960's. It makes for a perfect wall plate, or it would be a superior choice to add to an existing collection. 
 
Each plate measures approximately 9" in diameter, and each plate is sold individually.  There are some minor shows of wear and tear, due to the vintage nature, yet aside from some minor crazing, these plates are in wonderful condition.