Each chemical composition can be assigned a label {'allowed', 'forbidden'} according to whether it passes these chemical filters for inorganic compounds. They can also be labelled as {'known', 'unknown'} according to the presence of that composition in the Materials Project (MP) database. The entries considered here were retrieved via the MP API (v2023.11.1) using an anonymised formula notation (e.g. AB2), ensuring a consistent approach to formula representation. We can then categorise each enumerated composition according to their combination of labels: standard {'allowed', 'known'}; missing {'allowed', 'unknown'}; interesting {'forbidden', 'known'}; and unlikely {'forbidden', 'unknown'}.