This is a perfectly formed Dot Mold Jumbo Roller.

The name 'Dot Mold' comes from the number of dots in the glass that are a result of vent holes in the mold used to produce these floats.  If you look close, you can see 2 dots on top of the barrel and 2 dots on the bottom.  There are also 2 single dots on the non-seal end.  So, that makes a total of 6 dots visible on this Dot Jumbo. 

The Dot Mold Jumbo is the rarest of the 4 main styles of Jumbo Rollers (only the Flat-Bottom Jumbo Roller is more rare with 3 examples known to exist).

It's also presumed that Dot Mold Jumbos are the newest style of the jumbo rollers.

This Dot Jumbo is a wonderful emerald green color.

It measures 19 inches long and the barrel of the float is 8 inches in diameter.

There are signs of use with a couple of chips on the seal.  It was purportedly found in Oregon, USA.