Long thought by many to NOT have milk spots, I just got this proof in the two coin APMEX set yesterday: I haven’t yet tried the usual restoration methods which I imagine have poor results & might have to try that electrolysis even. Really disappointed though.
Sorry about the spots. What are they made of? Clearly this is not toning. Have you heard of Sodium Thiosulphate? I've used it to treat ancient coins with horn silver deposits. It is very effect in doing that. I don't know if it would be effective with milky spots. The process is simple: heat up some distilled water with some Sodium Thiosulphate (usually in the form of small tablets). Immerse the coin for perhaps a minute at most. Rise the coin with distilled water, dry carefully holding the coin is a soft cloth, and assess. Repeat if needed. Again, I have never tried this with a proof that has milky spots. There's a chance that it will have no effect. You might want to experiment with a low value coin with this problem first, using a low concentration and proceed from there.
Hard to say as it appears to be a blueish-gray haze. I have quite a few libertads and no others have this. Thankfully the reverse proof is NOT affected. BTW, still looking for a 2020 Libertad onza reverse proof.
I see. Actually I've seen this before with Libertads, but have not examined them closely. If the problem with due to a chemical reaction that has actually etched into the surface of the coin, then removal seem quite problematic, especially with a proof coin. I don't know if the Sodium Thiosulphate will help, but as I suggested you might try to experiment with a low value coin that has the milky spot problem, if you have one.
