Two large ancient gems have been set on the left- and right-hand sides of the trapezoidal panel in the centre of the shrine. They used to flank the Ptolemy Cameo, which was stolen in 1574 and is now in Vienna. The intaglio depicting Venus and Mars on the left-hand side may seem somewhat out of place on a Christian shrine until one considers that such precious gems were set in reliquaries because of their value. The scene or person depicted in these gems was either of little importance or was re-interpreted to fit Christian beliefs. Such ancient works of art often served as a template for medieval artists. The design of the robes worn by the Magi on the front of the shrine were modelled on the garments worn by Venus in this intaglio.
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