What exactly is a "Verbal Note ?

Hello everyone,

I am currently working intensely on my family history and verifying the Polish citizenship of my great-grandfather. During the interwar period, he was known to both German and Polish authorities, as he had submitted various declarations of option under the German-Polish Vienna Agreement of 1924.

While reviewing the relevant archival records, I have encountered the term "Verbal Note" several times. My documents refer to a communication from the Polish Legation in Berlin, in which his option for Poland was officially declared invalid.

Since I would like to classify this document as a key piece of evidence for my citizenship application, I have two questions for the experts here:

1. What exactly is a "Verbal Note" in this diplomatic/administrative context? Is it a legally binding document that officially records a person's status, or is it more of an informal correspondence between authorities?
2. What is the evidentiary value of such a note today? Can I assume that such a Verbal Note is filed in the archives of the Polish Legation or in corresponding collections as an official document regarding the affairs of my ancestors?

I would appreciate any information on the classification of this term, as it appears to be the crucial link in my documents between the disputed status and the actual clarification of citizenship.

Thank you very much in advance for your help!