The Onstelde-Zee and Brandt's biography seem to be a mixture

I actually have a number of texts from the 17th Century. I have the handwritten "Staet van Oorlog te Water" for 1628, 1629, 1631, and 1633, the Onstelde-Zee (1654), pages from Hollandsche Mercurius, Brandt's biography of De Ruyter (1687), and Aitzema's Saken van Staet in Oorlogh. These all seem to be in a mixture of "Middle Dutch" and "New Dutch". "New Dutch" preceded "Modern Dutch". Both of these had different spellings and different words than what is in "Modern Dutch". I discovered this website, today, that addresses the history of the Dutch language. This is on the University College London website. There is a related Dutch website, as well, the The Nederlandse Taalunie.