Kimo and everyone else thanks so much for your insight.
I acquired this cover in a U.S. collection - It was the only cover in the collection. I figured this to be a bonus that came with because I do not collect covers (yet

)and cant really put a "cost paid" on it.
After holding the stamp/envelope to a bright light (the envelope is loose, no longer glued together) It appears that the toning around the edges carries through pretty evenly behind the stamp. Thus making this cover seem more dubious.
I am going to send it in for an opinion.
If the opinion comes back negative (as suspected) my next dilemma will be to leave the stamp on the cover or soak it off?
Harry