While the literature on coronoid hydrocarbons is comprehensively surveyed, new enumeration results on select coronoid classes are presented. The first examples of Kekulean polycyclic (even-carbon) alternant hydrocarbons with doubly degenerate zero eigenvalues at the HMO level are identified. The parallelism between a molecule removed and the antimolecule hole left in formation of a graphite vacancy defect is elaborated. It is argued that the formation of a single carbon atom vacancy hole defect in graphite should be facile because it would entail a minimum electronic reorganization. These results are supported by a substantial amount of eigenvalue calculations. This work provides a unique overview for the class of coronoid hydrocarbons.