ARMY TM 9-2815-259-24P AIR FORCE TO 38G1-125-4 MARINE CORPS TM 09249A/2815-24P/4 xi (4) Fourth.  Refer to the Repair Parts List for the figure to find the part number for the item number noted on the figure. (5) Fifth.  Refer to the Part Number Index to find the NSN, if assigned. b. When National Stock Number or Part Number is Known. (1) First.  Using the Index of National Stock Numbers and Part Numbers, find the pertinent National Stock Number or Part Number.  The NSN index is in National Item Identification Number (NIIN) sequence (see 4. a (1)) . The part numbers in the Part Number index are listed in ascending alphanumeric sequence (see 4.b).  Both indexes cross-reference you to the illustration figure and item number of the item you are looking for. (2) Second.  After finding the figure and item number, verify that the item is the one you're looking for, then locate the item number in the repair parts list for the figure. 7.  ABBREVIATIONS. Abbreviations Explanation BOI   Basis of Issue DS    Direct Support GS    General Support MAC Maintenance Allocation Chart NIIN National Item Identification Number (consists of the last 9-digits of the NSN) NSN National Stock Number RPSTL Repair Parts and Special Tools List SMR Source, Maintenance and Recoverability Codes SRA Special Repair Activity TMDE Test, Measurement and Diagnostic Equipment UOC Usable on Code