This relief must have been one of a series that decorated a public building or perhaps a grand funerary monument. The iconography derives from a passage in The Iliad that describes the Nereid Thetis, mother of the hero Achilles, and other Nereids carrying newly forged armor to her son.
#1245: Marble lunette with Nereid riding Triton, Part 2
von Bothmer, Dietrich, Carlos A. Picón, Joan R. Mertens, and Elizabeth J. Milleker. 1993. "Recent Acquisitions: A Selection 1992–1993: Ancient World." Bulletin of the Metropolitan Museum of Art, 51(2): p. 16.
Metropolitan Museum of Art. 1993. "One Hundred Twenty-third Annual Report of the Trustees for the Fiscal Year July 1, 1992 through June 30, 1993." Annual Report of the Trustees of the Metropolitan Museum of Art, 123: p. 29.
Picón, Carlos A. 2007. Art of the Classical World in the Metropolitan Museum of Art: Greece, Cyprus, Etruria, Rome no. 425, pp. 366, 488, New York: The Metropolitan Museum of Art.