Stickers like that were and are generally for internal use, like it was rechecked for proper torque, or it could denote what line it went down for engine assembly. If you look at most new Fords you'll see stickers and or grease pencil markings on the engines, trannies, bodies and the frames. Most of them mean it was looked at and checked at a certain QC station, or there was a repair. Heres me working hard...looking for the next grease pencil mark!