This ebay auction is for a pair of very early Western Electric 555W drivers in good shape. They may even be NOS. Only the earliest ones have the mesh covering over the rear opening; later ones have a solid plate.
It will be fun to see where this one ends. Price is already up to $5,750, with 14 hours to go.
http://cgi.ebay.com/ws/eBayISAPI.dll...0863&rd=1&rd=1