Show us a photo of the machine. 1981 is pretty early for an FP4NC.....Wondering if this is a "rounded Head" machine.
Only three user printed doccuments as far as i know.
1. Orange book (electrical documentation) has schematics for boards, wiring layout and component locator to show where different electrical parts are located.
2. User manual: has operational information and programming examples along with specs for the machine.
3. Parts book: shows mechanical parts and part numbers for the machine.
Assume you are looking for the parts book....But it would be nice to confirm what machine you actually had.
Cheers Ross