I would agree that it is for repairing the flare seats on brass fittings. Should be for 45 deg. Flares.
It looks like the outer threaded portion should be free of the inner portion. That way you can screw it on to the damaged fitting and turn the tee handle to reshape the flare.
The one without the outside shell might be an extra, if the same size as the other one, or maybe you use it free hand if the flare isn't munged up too bad.
Just an idea.
Mike