Quote: "internal components would only have part numbers."
In fact, many internal parts have MSN numbers (Manufacturers serial numbers). These may be ink-stamped or etched near the part number and are often on every part of an assembly that has room. They are not on the ID plate for an assembly but will normally be nearby, along with the assembly part number. One might see the format 285T 1234567 MSN 789 or similar. All these should be traceable through documentation. Its a long time since I worked with Boeing products, or any others for that matter and cannot now recall the precise format. It is almost certain that some of these numbers cannot be seen without completely disassembling a component, hence it may take a long time.
Not sure how old this is but it may contain some relevant info
http://www.thermark.com/TM_Downloads...613-2_XXXX.pdf Page 23 shows the method of marking.
Boeing 777 would be 285Wxxxx not 285Txxxx