A little over 200 years ago an anonymous 18th-century herbarium was bought at auction by the National Library in The Hague. Until recently, not only did nobody know where this herbarium originated, its mystery was also surrounded by its content, beautifully dried plant specimens accompanied by garbled names. In 1868 it was handed over to the National Herbarium in Leiden (later incorporated in Naturalis Biodiversity Centre). The lack of scientific attention seemed at odds with the beauty and the possible historic relevance of this herbarium. We studied 796 digitised specimens, identifying 618 unique plant species in the process. Remarkable was the high number of exotic-, and non-medicinal, indigenous species. By determining their native range, comparing the herbarium with other, contemporary herbaria, studying paper and bindings, retracing the identity of one-time owner Simone D’Oignies, and in particular tracing the origin of the names, we were able to assess when it was made and what the scientific and societal value was. Our initial impression - that the D’Oignies herbarium was a garden herbarium - was eventually confirmed by information that upon his death, Jakob Ligtvoet (1686-1752), head gardener of the Leiden botanical garden, owned a herbarium with all the characteristics of this herbarium. Comparison with its twin herbarium, the Zierikee herbarium, convinced us that – contrary to earlier research by the author - it was the D’Oignies herbarium that matched the description of the herbarium once owned by Ligtvoet. However, both were created and kept by the gardeners of the Leiden botanical garden.