Parmigiano Reggiano: PDO for 400 years

It is well known that Parmigiano Reggiano is a PDO (Protected Designation of Origin) product, a certification that guarantees that a food product is processed in a specific location.
Our cheese obtained PDO certification in 1955 and at European level in 1996, but several centuries ago there was already a need for a document to certify its authenticity.