From new.math.uiuc.edu/oldnew/calculart/
This surface is a Whitney-stable 3D projection
of a nonorientable surface with Euler
characteristic 0 (a Kleinbottle) embedded in
4-space. Like Steiner's Roman Surface,
the Etruscan Venus loses its singularities
under François Apéry's Romboy homotopy
and becomes an immersed surface equivalent to
the connected sum of two copies of Boy's Surface.