I figured out more about this device. It appears to be specifically made to fix stripped inlet carbs by squeezing an o-ring to make it seal. Red arrow points to a nut, and blue arrow points to the o-ring. quadrajetparts.com has a squeeze-type repair device that does the same thing but looks a little different.
http://quadrajetparts.com/ring-inlet...ing-p-382.html
This type of repair device requires an in-line filter since it occupies the built-in filter housing.
I have a fat barb adapter for hose, but it appears to accept a standard steel line flare fitting.