Friend has this quarter that they have already done an acetone bath and no results. Any ideas what the next step is or is it a loss in collectability? Here's his pics.... (Also, don't know what the gunk is either).
To answer your question, no, I don’t think it can be saved. In 1964, 90% silver planchets were routinely washed before being fed into the stamping press, cleaned with detergents and a borax solution, then rinsed. ANY remaining residue remaining after the final rinse eventually produced silver chloride, a product of the cleaning agents being trapped under the surface of the silver, and over time produced milk spots or blotches. This 1964 Washington appears to have missed a final rinse. Franklin Halves are notoriously known for milk spot problems as well. Professional conservation may be able to reverse this malady, but I don’t have any knowledge or experience in this type of rescue action.
I’m sorry to say that the damage is beyond repair. It looks like the coin was dipped and not rinsed off properly.
