The Trombonium is essentially an upright valve trombone.  It was popularized by Kai Wilding and JJ Johnson in the 1960s in several jazz albums (see photo below).  Several companies - including King and Conn - made versions of the trombonium. It has the same brassy sound of a trombone with perhaps a bit more mellow edge. The bell is removable and can be rotated to give a different sound. Inscribed on bell: