A private museum operated through a foundation files an annual return with the tax authority of its jurisdiction. In most cases the return is public. It names the trustees, the related parties, the significant donors of the year, the acquisitions made, and the values assigned to non-cash gifts. Together they describe the collection and, by extension, the collector.
A family office reviewing a counterparty who founded a museum will find in the annual returns a directory of the counterparty inner circle, dated by their tenure as trustees, and a list of every significant piece the foundation received during the reporting year. The trustee list is a proximity map; the acquisition list is an inventory.
The returns disclose non-cash gifts at the appraised value at the date of transfer. Acquisitions made with foundation funds disclose the seller and the price. Related-party transactions disclose loans, sales and services between the foundation and the founder other vehicles at the amount and terms. Each of these fields is required by statute in the major jurisdictions where such foundations operate, and each is reviewed by the tax authority before the return is accepted.
A private museum is a public filer. A reader who reads the returns has an unusually complete picture of the founder holdings, associates, and priorities in that year, filed by the founder in a form they cannot easily edit.