Years back, in a Mustang magazine, I remember reading about what happened to the stamping dies used by Ford to make sheet metal parts, fenders, hoods, body parts, etc. (A side note: It takes several different dies, a dozen perhaps, both male and female, to form the bends needed in a fender.) At the end of a production years' run, most were sold as "scrap" - aka worn out. The good ones went to companies that contracted to make service parts. For some reason of other, Canadian stamping companies comes to mind. After the dies wore out again, they went overseas, like possibly to India, Indonesia or Taiwan. Somehow, these dies were "repaired" (welded?) and continued to make parts that were not quite acceptable to Ford, but "sell-able" - to you and me. The date codes were a step, using a removable stamp/die set.
Jim