I'm enclosing a photo of half an insulator which might well be the rarest of all threadless. It is boldly embossed THAMES GLASSWORKS N. LONDON CT. The glass is a deep olive amber. 

This piece was from the famous Charlie Gardiner Bottle Collection that was auctioned off a few years ago. I talked to Norm Heckler, who appraised and wrote the catalog for the Gardiner Collection, to see if he could shed some light on the Thames Glassworks. 

According to Norm, who by the way, is an expert in the area of early New England glass manufacturing, there was a series of glass companies in New London, none of which was ever successful. Apparently the failure of one company brought about the birth of a new one, more than likely using the facilities of the previous company. 

The Thames Glassworks started business perhaps in the mid 1860's and lasted until the early 1870's. No bottle has ever been positively identified as being a product of the Thames Glassworks. So you can see, this is quite a mystery company. But there is no doubt that they did indeed manufacture glass insulators. 

I thought your readers would be interested to know such a piece did exist, although it would be rather difficult to assign a CD # to it. For those who write price guides or think about writing price guides, this was item #1326 at the Gardiner auction, and sold for $190.00. If by any chance someone picks one up at a flea market this summer, I'll be glad to pay $1000.00 if it's in very good condition (me and a hundred other collectors)!