The surface with three cross-caps (Francis and Collins 1993, Francis and Weeks 1999).
Dyck's Surface
See also
Cross-CapExplore with Wolfram|Alpha
References
Francis, G. and Collins, B. "On Knot-Spanning Surfaces: An Illustrated Essay on Topological Art." Ch. 11 in The Visual Mind: Art and Mathematics (Ed. M. Emmer). Cambridge, MA: MIT Press, 1993.Francis, G. K. and Weeks, J. R. "Conway's ZIP Proof." Amer. Math. Monthly 106, 393-399, 1999.Referenced on Wolfram|Alpha
Dyck's SurfaceCite this as:
Weisstein, Eric W. "Dyck's Surface." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/DycksSurface.html