La Cimbali Auto-frother
Not Pictured on any diagram (this version anyway). The fixing nut to attach to the valve is too short for any of the usual parts (spring, spring seat, o-ring) to fit into. We surmise that the fixing nut is installed onto the valve as tight as can be, effectively creating a mechanical seal of metal on metal. Little is known about this mythical device. What is it for? Should it not be returned from whence it came?