1958 Proof Penny - Please Explain "Shadow Lettering"

To me, it looks like that lettering is on the packaging

this could be from either shadowing in the photo or there may be some Machine Doubling here which is fairly common and has no added collector value. there a several ways this can occur.

Improper Die Seating
If the die is not fully seated in the press, it can move or bounce during the strike. This causes a secondary impression that pushes metal aside, producing a flat "shelf" effect

Vibration or Oscillation in the Press
High&-speed coin presses generate vibrations that can travel through the machinery. If these vibrations affect the die&-planchet contact, the die may shift slightly in the final milliseconds of the strike, creating a Mechanical Doubling.

Die or Press Misalignment
Even small misalignments between the die and the planchet can cause the die to move during the strike. This is more likely if the die is worn, loose, or if the press is not perfectly calibrated

Ejection or Shift During Strike
In some cases, the die may shift due to the ejection mechanism or mechanical "shift" in the press, especially if the planchet is not held firmly in place

Surface Metal Displacement
The shifting die displaces surface metal, creating a flat, uneven edge on the design feature. This is different from the rounded, offset images seen in true doubled dies

I agree, it's from the packaging.
. . Lettering is too far apart to be considered Machine Doubling.
https://www.coincommunity.com/forum...03-1-1-.webp