Pectoral

a square plate of gold or silver, either jewelled or enamelled, sometimes worn by English and, other bishops on the breast, over the chasuble, at mass. It is sometimes called a rationale or rational. Its use appears to have been common during the Middle Ages, for several examples occur on monumental effigies, but since the 14th century it seems to have been disused. It was placed round the neck, and hung on the breast, either by a chain of gold or by three or more silver-gilt pearl-headed pins.