Just read the NCS response. As I initially had thought , they will be able to offer some measure of benefit to restore this little lady . Hope you take them up on this Benj . Anxiously, I will be awaiting the " after " photo's .
Have a look through the many questions posted on ASK NCS From things I have read on that board in the past, NCS have had success removing haze and early state toning on proofs. Milks spots they consider struck in during minting and cannot (or will not attempt on customer submissions). Leads me to believe they have attempted to refine a process for treating milk spots but haven't one they are willing to use on submitted coins.
now see, that bugs me. The biggest problem with cloudy proof coins was the Mint and not the storage after they were sold. There should be some way to eliminate the haze, but maybe not
Here is an example of a Kennedy Half Dollar which exhibits the condition which you bring up here. http://coins.ha.com/common/view_item.php?Sale_No=1152&Lot_No=3852 and some conversation about this coin: http://boards.collectors-society.co...213082&Words=&topic=0&Search=true#Post4551688
Pose the question on NCS again. They answer it on a case by case situation. They need to see the problem pieces to give an idea if they can or cannot. Many times they indicate that they can restore some eye appeal even if they cannot completely remove the problem, which can improve chances of obtaining a higher grade.
There is, a dip in MS70 will remove the haze from Proofs in most cases. The problem is that sometimes that haze comes back. But it almost always stays clean long enough to get the coin slabbed.
Mikenoodle; yes NCS does restore hazy and cloudy proof coins. It is one of their specialties! I have seen the before and after results and it is absolutely amazing!