there are two questions: 1) Quartiermeister [marechaux-de-logis within your sources] normally belonged to the 'middle' ranks of prussian regiments; they were responsible concerning all aspects of logistics.
2) If you are just working on the Magdeburg capitulation, I think it will be that of 1806 with von Kleist. My question: are there more texts round about 'honorable capitulation' from 1806/07 to 1813/14 --> e.g. Wittenberg Jan. 1814 with Général La Poype; those texts could serve for detailed comparison. Besides that i would like to know if the capitulations were written only in french or also in a German version (perhaps to find within the huge archives of the Geheimes Staatsarchiv Preuß. Kulturbesitz at Berlin).
Concerning the intercepted letters from 1806 i will answer later on at the other thread.
Best regards, Eberhard K.