From inside (document excerpt):
Perkins · engines INSTRUCTIONS – CORE & OPTION PARTS BOOK The principles of using the Core & Option Parts Book are as follows: 1. One must first consult the Build List Section for the breakdown on the specific list. This breakdown has been layed out with the core initially, which generally has six sections, followed by the options, accessories and gasket sets.
Within each breakdown, a brief summary of the components is given for each core, option and accessory pack. Each pack has the page number on which you can find that specific breakdown. 2. Once the core, option or accessory pack number has been determined, it is then necessary to go to the applicable page. Each page is also marked at the top with its C & 0 pack (i.e. AFNT00175). The illustration for each specific page is opposite the page. The illustrations shown are as exact as possible. If a specific part is not shown, it is either supplied by the OEM or not required on this engine. The layout of the data shows the illustration number first, followed by the part number. The third column will sometimes list a number (i.e. #10) next to the part number (item #11). This signifies that this part (#11) is included in the assembly (#10). The fourth column will list a part number when that particular item is not serviced and you must purchase the assembly or repair kit. In this case, column #2 (part number) will be blank. The fifth column lists the quantity and the sixth column lists the description. 3. 4. r. J 4.108 Build List NAP000265 Index Issue 1 ACHEOO45 CYLINDER BLOCK BLOC – CYLINDRES
Wikipedia’s page for Perkins Engines