T=2* icosahedral capsid is composed of 12 pentameric dimers for a total of 120 capsid proteins.
The T=2* symmetry is an nonofficial appellation, to be rigorous the capsid has a T=1 symmetry with each unit composed of a homodimer.
D. L. Caspar, A. Klug
Cold Spring Harb. Symp. Quant. Biol. 1962; 27: 1?24