Charley,
After assembly ( and testing ) at the Tonawanda facility,
the engines were painted as they went down a paint line.
Accessories weren't added as of this time, so I would have
to think that the pad got painted. Shields ( vac-forms )
were used on the aluminum intakes to avoid overspray.
Possibly, the engine ID pad was oiled or masked in some way
to avoid paint. I would not think this to be the case though.
Steve