Drawing   numbers   may   be   used   to   identify microfilm that may be available on the equipment or assembly.  Some  large  assemblies  are  illustrated  in  IPBs but are not broken down sufficiently to show identifying data  for  their  component  parts.  By  obtaining  the drawing   number   of   the   larger   item   and cross-referencing  it  to  the  applicable  microfilm,  you  can obtain  sufficient  identifying  information  for  the component  part. Specification  Number A  specification  number  is  assigned  to  documents describing  the  characteristics  and  properties  of  material purchased   by   the   Federal   Government.   These specifications  are  used  by  purchasing  officers  to  ensure that all of the requirements for the material are met. Specification numbers on some support equipment are particularly useful when you are trying to procure component parts. Nameplate Some equipment has a nameplate attached that provides such information as the manufacturer’s name or code, make or model number, serial number, size, voltage, phase, NSN, and so on. This information is particularly helpful when you are requesting material that is not subject to the Federal Catalog System. MANUFACTURERS’ INSTRUCTION BOOKS Most equipment purchased for Navy imaging has with it an instruction book or a technical manual that is published by the manufacturer. You can often use it to help  you  identify  specific  parts,  since  this  technical manual often includes parts lists, detailed drawings, and specifications. ILLUSTRATED   PARTS BREAKDOWN Illustrated Parts Breakdown (IPB) publications are an  important  source  of  information,  particularly  for ordering  specific  support-equipment  parts.  Used properly,  they  provide  the  information  necessary  to identify a part number. In some cases, IPBs provide cross-reference data that can be used when the prime item requested is not in stock. An IPB is prepared by the manufacturer for most major  items  of  imaging  equipment  and  accessories. The IPB is designed to enable supply and maintenance personnel to identify and order replacement parts for equipment. Procurable assemblies and detail parts are illustrated  and  listed  for  quick  identification  of assemblies and their component parts. The items are arranged  continuously  in  assembly  breakdown  order. The illustrations are placed as near as possible to their appropriate listing (fig. 5-6). Although slight variations in format exist among the various IPBs, each one includes the following major sections: The   INTRODUCTION   includes   general information about the equipment, contents of the publication, and instructions for use. You should refer to  the  introduction  before  attempting  to  use  an unfamiliar IPB. The GROUP ASSEMBLY PARTS LIST consists of a   breakdown   of   the   complete   unit   into   major components,  systems,  installations,  assemblies,  and detail parts. Generally, parts are indexed in disassembly order.  In  some  instances,  assemblies  or  installations  are shown in assembled form in one figure and the detail parts are illustrated in another figure. The NUMERICAL INDEX lists part numbers in alphanumerical  order,  and  each  part  number  is cross-referenced to the figure and index number where it is shown. This section also shows the total quantity of each part used in the equipment, material source code, and NSN, when applicable. The REFERENCE DESIGNATION INDEX lists, in   alphanumerical   order,   reference   designators (example: B1, J1, K7, and so on) on schematic and wiring  diagrams.  The  index  also  lists  part  numbers  and index numbers to indicate where the parts are located in the  IPB. CONSOLIDATED MASTER CROSS-REFERENCE  LIST The  Consolidated  Master  Cross-Reference  List (C-MCRL) is designed to provide a cross-reference from  a  reference  number,  such  as  a  manufacturer’s  part number, a drawing number, a design control number, and so on, to an assigned NSN. Part I of the C-MCRL is  designed  to  assist  you  in  identifying  items  in  the 5-8