Here is a rear view of this threadless insulator. It is Olive Amber Blackglass.

The account of the initial find can be read here:

http://www.insulators.info/news/thames.htm

and a more detailed article that appeared in Crown Jewels can be found here:

http://cjow.com/archive/article.php?month=2&a=02Thames%20Glass%20Works%20Insulator%20REVISITED.htm&year=1998

(photo courtesy Mike Doyle)