An extremely rare Tunbridge Ware bead that originally formed part of a necklace. The only reference I can find to a Tunbridge necklace is the picture, reproduced below, on page 64 of Brian Austin's book on Tunbridge Ware. Austin dates it to circa 1840. Roughly 3/4" dia.
The seller had two beads for sale. The other was much nicer, and sold for considerably more. I was underbidder on that one.
Bought from soopahoopa on UK eBay. Pictures from seller.