I'm very much not trying to be difficult or challenge a milk spot scenario, but if it was the result of an improper rinse of the planchet then why the big glob on the left side of the packaging in the original 2nd photo?
Near the top left of the pouch? I thought that was just another reflection like the one on the right...
The right does look like a reflection. The left looks like it has texture and depth. I really don't know for sure.
One source (Rick Tomaska- not sure which book) says that milk spots are soap residue left on the planchet because the planchets were not properly rinsed to remove all the soap. The soap residue is then permanently struck into the coin during the minting process creating the white spots. They cannot be removed, they are part of the coin. I have seen a coin with a milk spot that covered nearly the entire obverse.
Darryl I've looked at tens of thousands of original Mint and Proof sets over the years - I collected them for almost 40 years - and never once have I ever seen anything like what I'm seeing on these coins. Milk spots on some of the Proofs ? Yeah, I've seen that more than a few times. But what I'm seeing on these doesn't look anything like milk spots. But since I'm seeing what appears to be some kind of machine damage on the coins from counting or packaging, particularly the '62 - that's about all I can think of that it can be from - it makes me wonder if some kind of contaminant got on the coins during the process. I suspect that about the only way you're ever gonna find out what it actually is on the coins is to take samples and have them analyzed. Or send the coins to a lab and simply let them analyze it.
It practically looks like mold. And I also thought the big spot looks like spilled paint. I bet if V.Kurt were still here he might have some mad scientist formula to get rid of those Super Milk spots. Post acetone photos to see if there's a change. But I am thinking this is going to require a stronger dip.
I agree Doug, the green Crystal's easily flake off the coin and makes me wonder what crystallizes like this that would be introduced during the minting/handling process. Thank you for your thoughts.
Useless answer: An alien gobbed on it. Snarky, and equally useless, answer, with apologies to Bill Fivaz: I don't know, I wasn't there when it happened. Less useless answer in light of the previous one: It could be anything, as the mint operation is not a clean room, and 56 years is a long time to give contaminants on the surface of a coin, or transferred from the plastic, a chance to do their work. Related insightful advice: Never buy proof sets sight unseen.
picked these up for less than melt so no harm done. Didn't want to pass them off to someone else and an coin experiment is always fun and informative.