In the early 1960s Teletype took on the assignment of writing Bell System Practices covering their equipment. Previously Teletype had written its own customer manuals and then some office within the Bell System had turned them into BSPs. These later Teletype manuals consist of just the front cover and revision and contents pages, followed by the BSPs that make up the manual. The Teletype-written BSPs all have the "TC" suffix after the BSP number. In earlier times there were part numbers with embedded dashes. Magnets had part numbers like M-xxx and Bulletins had numbers like B-xxxx. When Teletype went to automatic data processing for handling parts orders they considered it necessary to get rid of the embedded dashes and letter prefixes. The letter prefixes were moved to suffixes: thus M-xxx became xxxM. Very late, Teletype started issuing Manuals instead of Bulletins, which resulted in xxxM being a part number that might be for a magnet for for a manual.