The will of the Duke of Windsor will be opened for copyright determination.

A court in the U.K. has ruled that the will of the Duke of Windsor, who passed away in 1972, will now be unsealed for for limited purposes, according to the Daily Mail in "Duke of Windsor's will to be unsealed at last… but only so The Crown's writers can get their facts straight."

King Edward VIII of England abdicated his throne in 1936, so he could marry a divorced American woman Wallis Simpson. This changed his title from king to duke.

The contents of his will were quickly sealed by the court and have never been made public, despite great public and historical interest in them. People are curious whether the will might shed any light on the man's decision to abdicate. 

The writers of the Netflix show The Crown would like to use the duke's letters in their show.  However, they first need to know who owns the copyrights to those letters, so they can get the necessary permissions to use them.

It is not likely the will's other details will be made public.

For a former king's will to be sealed, is probably a simple matter.

For other people, it is much more difficult since wills are generally a matter of public knowledge.

An estate planning attorney can advise you on creating an estate plan that meets your unique circumstances under the laws of your state of residence.

Reference: Daily Mail (Nov. 15, 2017) "Duke of Windsor's will to be unsealed at last… but only so The Crown's writers can get their facts straight."