5 One sheet of an elliptic hyperboloid of two sheets, in two pieces
An elliptic hyperboloid is a solid or surface, some of whose plane sections are hyperbolas, while others are ellipses. If no elliptical cross-section goes around the conjugate axis of any hyperbolic cross-section, the hyperboloid has two sheets. The other sheet would be an inverted model placed symmetrically above this one. The hyperbolic vertical cross-sections can be seen at the flat end and by separating the pieces. The elliptical horizontal cross-sections can be seen on the base.