It looks like something stuck to the surface, 90% silver coins are not plated in any way. So, plating is out of the equation.
When you first see this coin plating comes to mind. But then use see the days and that’s a 90% silver coin so it’s not a plating issue at all. Sure a lot of copper showing so I’m thinking it has someone on the surface or the copper didn’t mix with the silver correctly. Be sure to keep and protect this one.
its definitely indented and follows the curves of the design, you can see the same damage more lightly under the lettering at the top reminds me of tarnishing in that area
That is an interesting coin. Thank you for the post. Maybe @Fred Weinberg, @JCro57, or others might chime in.
Maybe some angled shots might help, but honestly a soak in some acetone or even distilled water would be a good start.
Not sure why ED. This still looks like some corrosion, and it is raised. A soak in water or acetone is not considered cleaning. Vigorously rubbing the area in question while you are restoring a coin would be considered cleaning. That being said a soak is a good start. If you use acetone, rinse afterwards in distilled water to remove any left over contaminants. The distilled water followed by a pat dry with a soft towel (no rubbing) will also eliminate any water spots. In the end the acetone may not even remove what we are seeing just a heads up. And if you are uncomfortable then don't try the process, take it to a dealer and let them decide what it is, and if it is worth any effort.
