Receipts for the spinel cation-decoration count: 15 spellings of 2 Co among 6 cation sites of the spinel primitive cell give exactly 3 isometry classes. Three independent quotient methods agree; inversion and site-order controls pass; real-material controls (ZnFe2O4 normal, LiFe5O8 ordered inverse P4_332, Fe3O4 valence-blind) read as published.