What symmetry did Klug and Finch report for polio virus after Franklin's death?

Klug and Finch reported that poliovirus has icosahedral symmetry after Rosalind Franklin’s death. Their 1959 work continued the virus-structure research begun by Franklin and her group at Birkbeck College.

Franklin turned to poliovirus after making major advances on tobacco mosaic virus and other plant viruses. She and her colleagues used X-ray diffraction to study the virus in crystalline form, but her rapidly failing health prevented her from completing the project. Franklin died in April 1958; Aaron Klug then succeeded her as group leader, working with John Finch and Kenneth Holmes.

The team eventually obtained highly detailed X-ray images and published their findings in June 1959. An icosahedron is a geometric solid with 20 triangular faces and 12 vertices, a compact arrangement that allows viral capsids to be built from repeated protein units. “Cubic symmetry” can sound plausible because an icosahedron belongs to the broader cubic symmetry family in crystallographic terminology, but the canonical answer for poliovirus is icosahedral symmetry.