No. 787. Angular hoop, projecting sharply below the shoulders, which are in the form of hollow leaves within a triangular frame. The bezel is square and contains an octahedral diamond; the sides are open and form a kind of wave pattern. Castellani Coll., 1872. 3rd century, A.D. No. 788. Type akin to last. On either shoulder is an openwork triangle. The bezel is square and contains an octahedral diamond; on either side of the bezel is a small openwork triangle. No. 789. Type akin to last. The lower part of the hoop has a groove running along its middle; either shoulder is cut away in a slight curve. The bezel is square, with a triangular space left open in each side and with a round opening below. It contains a diamond of octahedral form. Franks Bequest, 1897. No. 790. Type akin to last. The hoop is rounded without; the curved excision of the shoulders is more pronounced. Two double pyramid-shaped (octahedral) diamonds are set in the bezel. A triangle is cut out of either shoulder, and two smaller triangles on either side of the bezel. Underneath the stone are two lozenge-shaped openings. Franks Bequest, 1897. [Illustration: PORTRAIT OF AN UNKNOWN MAN IN THE COSTUME OF THE FIFTEENTH CENTURY, BY ANTONIO DEL POLLAIOLO He holds between the thumb and index of his left hand a ring set with a naturally pointed diamond crystal Galleria Corsini, Florence] [Illustration: PORTRAIT OF A VENETIAN SENATOR, BY A. DA SOLARIO Seal ring on thumb of left hand National Gallery, London] In all these cases the diamond is a small natural crystal of octahedral form suggesting the “diamond, a point of a stone,” of which the astronomer Manilius wrote in the first century, and, perhaps, the diamond in Berenice’s ring mentioned in the same period by the satirist Juvenal. Another ring in the British Museum, however, is set with two _facetted_ diamonds, as well as with two other stones (No. 778 of catalogue, Plate xx, same number). Here the diamonds have unquestionably been set at a time long posterior to the making of the ring, which is believed to belong, approximately, to the same period as the others we have listed. The diamonds were probably inserted to replace two of the original stones that had fallen out of their settings. Sir Charles Hercules Read pronounces the instances of diamond settings in ancient rings to be exceeding rare. He states that the examples above noted are the only ones of which he knows, and considers that they belong to the third or fourth century of our era.[162] The famous Marlborough collection of gems includes a thumb ring entirely of sapphire. To give this stone ring the necessary resisting power, it has been lined with a thick hoop of gold. The engraving it bears, a head of the Elder Faustina, the wife of Antoninus Pius (86–161 A.D.), is believed to replace an original Arabic inscription that fitted this ring for use as a seal.[163]