"Two confronting sphinxes representing Horus and Seth"
Pectoral Ornament, Middle Kingdom, Dynasty 12, probably reign of Senwosret II or Senwosret III, 1897-1841 BCE (perhaps from Dahshur)
Electrum with remains of lapis lazuli, carnelian, and amazonite inlays; H. 1 1/2 in. (3.8cm)
Myers Museum, Eton College

There's several Set sightings in Wilkinson's _Reading Egyptian Art. I was able to find a better picture of this one on the web.

This was from a special exhibition at the Metropolitan Museum of items from Eton college. Sadly, the Eton College Myers Museum "closed permanently and will not re-open." Where these pieces will go next, I do not know. I did track the ‘The small masterpieces of Egyptian art’ at the Rijksmuseum van Oudheden from 7 November 2003 until 29 February 2004. But where now, that is a mystery.