Linda, the tape is on the right side of the cover. It reminds me of the vintage needle plates that have had tape set for years and dried up the top layer which comes off easily, but the adhesive has dried and hardened. It looks like maybe duct tape or the wide scotch tape remains.
The grease on the cam stacks is shiny and probably was just done. If it was old it would be a different color, and probably different pattern of remaining grease. Also at least it is not the white lithium type, however that is what is being recommended for modern machines.
Janey - Neat people never make the exciting discoveries I do.