It's widely known that mark WP #116 'TO in a Diamond' comes in many beautiful colors.  There's also a version of this mark that comes in the standard blue-green color. 

These blue-green floats are a little large than the colorful versions of TO; measuring about 3 1/2 inches in diameter.

This particular float has a well-centered stamp that shows all points of the TO mark.

The float is slightly out-of-round and is made of thick heavy glass.