The Stadsarchief help says (translated):
Estate papers are papers from the parental estate of an orphaned child. It can concern a wide variety of documents. In addition to documents related to the parents, such as marriage certificates and burial records (cemeteries) of the parents, inventories of the division and/or sale of the parental estate, the files may also contain personal papers of the orphan. These are, for example, a certificate of baptism, proof of vaccination against cowpox and registration of a male orphan for military service.
These estate papers come from the archives
of the Reformed Municipality in Amsterdam,
specifically from the archives of the Diaconie orphanage
(inventory numbers 465-683).