A friend of mine picked this up a few months ago at an estate sale and wanted to know if it can be restored and still get a good grade if he has PCGS restored and recapsulate it with a grade. Sorry about the duplicate photos.
It's only about 35% silver, the rest nickel and manganese. There were 120 million minted, so don't put much effort into "reshining" it. As above acetone or some silver cleaner to dip it, and you shouldn't even think about certifying it or having someone clean it for you. The cost to have anyone else clean it up would/will be over 10 times what to coin will ever be worth. Just keep it as an oddity.
The cost to conserve will outweigh the value of the coin many times over. You can try a little acetone, not mail polish remover, but pure acetone.
As noted, conserving the coin may be of interest, but TPG activities and costs are out of scope. Do a search here on coin conservation...you'll find many valuable tips. Using the least damaging to start is my suggestion. As some have noted here at CT, soaking in distilled water is a fine place to start. Timing and cycling should be kept in mind, especially as you escalate the process/materials. Our Ancient coin collectors here likely have the most experience. At some point, conservation gives way to cleaning, which generally diminishes the value and interest in a coin. You can bet the TPG will notice.
The answer to your question "Can it be restored?" largely depends on what is wrong with it. If it is just a surface film, a spot of something on the coin, the coin can be conserved - that is, the film or spot can be removed. I'll let others describe the methods. However, if that spot is actually corrosion and has damaged the surface of the coin... no, there is no way to restore that and have it be acceptable to the majority of collectors. For extremely rare coins, there are techniques to minimize the visual impact of the problem, but it will always be a damaged coin.
