This stain needs to go!
Insider2
Posts: 14,452 ✭✭✭✭✭
Before conserving this Franklin I removed a chunk of foreign matter that was stuck to its surface. It was attached long enough to react with the silver. You can see an outline of the the brownish debris in the center of the whitish stain. This coin can be returned to its original condition with some chemicals. Acetone did not work either to dissolve the debris or remove the stain. 
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Xylene?
Acid?
Liquid nitrogen? Phaser set on stun?
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If acetone did not work, it must not have been organic...any idea as to what it was?? Cheers, RickO
There is a good chance that the surface has been etched and it can't be reversed. Whatever it was probably reacted with the copper content of the coin.
I was just checking in to make sure you weren't un-toning any gold coins!
Nope? It would be nice to be able to analyse the different types of crude on coins. It would make a great article/study.
Luckily, not this time.
If you take the stain and rotate it then move it over the damaged area of the left (blue circle) bell hanger, you get an almost perfect match. I would say your stain was three-dimensional organic residue that moved.
Nice re-imaging, Intueor.
Pete
Optical Detective @Intueor!
Thanks! Excellent detective work and a very informative post! I wish I knew how to do that stuff. How did you figure out that the debris was once in the center of that whitish spot in the first place? I wonder what caused it to move before it was imaged and posted?
Sorry for the delayed response....
Thanks for the compliments but, truth be told, I have seen this type of ugly organic damage on many Franklins. After using plastic tipped "picks" or compressed air to remove the "junk", that tale-tail damage "whitish splotch" usually hides underneath. When I saw your image, it was just a matter of connecting the dots. Can not say how it moved and my scenario is just conjecture. The actual technique used to create the altered image is referred to as a "Lasso" to select a variable bordered detail and then rotate and move the "lasso selected" pixels. The white "void" is automatically created when the selected pixels are moved.