I'm assuming that this is some sort of Lacquer or glue with the reverse pressed into it from another penny? It isn't pressed into the penny, just into the goo. Thoughts?
Nope.. He gave us the clue.. In goop It was glued with another cent and separated leaving an impression. Remember that fkr future reference
Just for the learning experience, do an acetone soak and use a wooden tooth pick to remove the "goop."
Another clue is that the secondary devices and letters are reversed and incuse. (If it dissolves in warm water it might be some type of sugary water from a cup holder, as opposed to glue.)