Geometric Model by A. Harry Wheeler, Congruent, Symmetric Spherical Traingles

This cut and glued transparent plastic model shows two perpendicular spherical discs which might be considered to be representations of the equator and a meridian disc of a sphere. Another half-disc also is perpendicular to the equator and rotates on the line joining the poles. Two symmetric congruent spherical triangles are on the same side of the model as the half-disc and pass through what might be considered the North Pole. A sticker on the model reads: C, S, SA. A mark next to the reads: PT.