Now this one is a bit obscure, but I love it. Any takers?
Any fans of the Tudors might have had an idea about this one. It is a circa 1500 English court collar chain.
Chains of this sort became popular in the English court starting in the 14th century and often carried a pendant that indicated a particular allegiance or membership. I first became interested in the S-linked chains when I first encountered Hans Holbein (the younger's) hauntingly realistic portrait of Sir Thomas Moore at the Frick Collection. View it in person if you can. It is amazing.
Detail of Moore's Chain via Google Art Project