The Tools of Knowledge database is derived from SIMON (Scientific Instrument Makers, Observations and Notes), a database collated by Dr Gloria Clifton at the National Maritime Museum, Greenwich, drawing on and adding to data created by Project SIMON (see Clifton, 1991, [https://doi.org/10.1179/isr.1991.16.1.16]. The data was cleaned and remodelled by the Tools of Knowledge project to align with an extended version of the CIDOC-CRM cultural heritage ontology, called SIMEON. The SIMEON ontology [https://nms.iro.bl.uk/concern/datasets/2e8971bb-c46f-4725-b78d-e3468175a2f0] was developed by the project to better capture the specific types of entities and relationships present in the SIMON data, and to facilitate linking with other datasets.