Code TM   10-3930-660-24P Explanation AO- (Assembled by org/AVUM  level) AF- (assembled by DS/AVIM  Level) AH- (Assembled by GS  Category) AL- (Assembled by SRA) AD- (Assembled by Depot) Items with these codes are not to be requested/requisitioned individually. The parts that make up the assembled item must be requisitioned or fabricated and assembled at the level maintenance indicated by the source code. If the 3rd position code of the SMR code authorizes you to replace the item, but the source code indicates the items are assembled at a higher level, order the item from the higher level of maintenance. XA-   Do not requisition an “XA”-coded item. Order its next higher assembly. (Also , refer to the NOTE below.) XB -   If an “XB” item is not available from salvage, order it using the CAGE and part number  given. xc -   Item  is  not  stocked. Indicates  an  installation  drawing/diagram/instruction sheet/field service drawing is/are available for use. Order an “XD” - coded item through normal supply channels using the  CAGE and part number given, if no NSN is available. NOTE: Cannibalization or controlled exchange, when authorized, may be used as a source of supply for items with the above source codes, except for those source coded “XA” or those aircraft support items restricted by requirements of AR 700-42. (2)  Maintenance  Code. Maintenance codes tell you the level(s) of maintenance authorized to USE and REPAIR support items. The maintenance codes are entered in the third and fourth positions of the SMR Code as follows: (a) The maintenance code entered in the third position tells you the lowest maintenance level authorized to remove, replace and use an item. The maintenance code entered in the third position will indicate authorization to one of the following levels of maintenance. Code Application/Explanation c -Crew or operator maintenance done within organizational or aviation unit maintenance. o -Organizational or aviation unit category can remove, replace and use the item. F -Direct support or aviation intermediate level can remove, replace and use the item. H -General support level can remove, replace and use the item. L -Specialized repair activity can remove, replace and use the item. D -Depot level can remove, replace and use the item. 3