This intricately pierced necklace section is delicately worked in a technique know as opus interrasile. This lace-like technique became popular in the late Roman and Byzantine period, particularly for necklaces and bracelets.
For a section of the same necklace with a similar leaf motif, as above, cf. exhibition catalogue, In the Wake of Alexander: Jewellery from the Eastern Empires of Greece and Rome, Jack Ogden Ltd., London, 17 November - 1 December 1982, no. 25, front cover illustration; another section of this necklace is now in the British Museum.
Cf. J. Ogden and S. Schmidt, "Late Antique jewellery: pierced work and hollow beaded wire", Jewellery Studies, 4, 1990, pp. 5-12 for a discussion of the technique; J. Ogden, Jewellery of the Ancient World, London, 1982, pp. 19, 43-44, col. pl. 3 for a pierced work bracelet; F. H. Marshall, Catalogue of the Jewellery, Greek, Etruscan and Roman, The British Museum, 1969, pp. 330-331, no. 2817, pl. LXV, for two pierced bracelet sections with hunting scenes; R. Bland and C. Johns, The Hoxne Treasure, The British Museum, 1993, col. pls. on pp. 6, 8 and 20-22 for a group of opus interrasile bracelets with similar motifs to those on the necklace in the above lot. Also, C. Johns, The Jewellery of Roman Britain, London, 1996, pp. 116-7 and 194-5, fig. 5.31, pl. 11 for the Hoxne bracelets and technique "Pierced work of this nature is one of the outstanding achievements of Roman and Byzantine goldworking, ...".