You asked us: I have found a book call number and this number starting with M-35506-U. What is an "M" number?

MSFRIC collection houses nearly 530,000 military documents, in addition to other resources. These documents include student papers, DOD reports, agency studies, and policy directives for the military. "M" numbers identify these unique resources. Furthermore, the "M" number prompts our users to go to the Document Loan Desk to retrieve needed items. The Document Loan Desk is located down the hall in the east wing. A security clearance, the "need to know" and proper identification are required each time a patron wishes to use a classified document.