On an idle internet search I came across the following - The Duchy of Cornwall: Its History and Administration, 1640 to 1660 by Mary Coate Transactions of the Royal Historical Society, 4th Ser., Vol. 10, 1927 (1927), pp. 135-169 doi:10.2307/3678408 (35 page article).
Click on the image for a closer look.
I have as yet not been able to pin down a complete copy of the text and suspect parting with cash may well be required. The material is included in JSTOR, an online journal archive made available to researchers through participating libraries and institutions: JSTOR
A question that this rare article raises in my mind though is why there is not more material produced by independent academics available to the public on the history, development and roles played by the Duchy of Cornwall? Surely the Duchy would provide a rich subject matter for historical study? Why has our institute of Cornish studies not undertaken a complete examination of the Duchy and produced something for the public?
The map above shows Duchy property and foreshore. Not bad for a private estate! But what arguments where used to obtain the rights over the Cornish foreshore marked in yellow? Two forum threads on this topic: Cornwall 24 and This is NOT England