Documents covering the whole history of the value, not just its final form: corporate ownership records, auction and property sale documents, loan discharges, tax filings across the years, and an unbroken bank trail into the enterprise.
Prove the years, then the transfer
Hypothetical example: a Grand Bay-Westfield owner offers a single bank statement showing the balance after his fleet auction and the sale of his terminal property. That answers where the money is and not where it came from, which is the question.
A complete file starts with the incorporation and share records showing he owned the business through the period, adds tax filings for the company and for him personally across those years, then the auction house settlement statements, the property closing statement and title history, the discharge of the equipment loan and any mortgage, and finally the bank records for every account the funds touched on the way to the enterprise. Older records are the ones most often missing, so start the retrieval with the accountant, the lender and the registry office before anything is filed.