First off,

Here are a couple pointers.
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I have even seen Ebayers selling empty coin holders and COA for annual proof coin sets.
What's wrong with that? Some people like to organize their collection by having the boxes and COA's, and there's nothing wrong with those auctions as long as the seller clearly indicates the boxes are empty.
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So if a seller has many sales and an excellent feed back record,
A better method would be to focus on the coin, and not completely on the seller.
Quote:would the newer (1980s and newer) commemoratives be safe on
ebay.
There aren't certain groups of coins where you're guaranteed not to get ripped off or get a problem coin. Some series pose less risk than others, but for all coins and sellers the risk is there, you just have to learn to avoid those risks.
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I also noticed that commemoratives are also being offered after being graded and in the graders holder.
Those are known as Third-Party Graders, or
TPG's. The main four are PCGS, NGC, ANACS and ICG. Some pros include that those coins are guaranteed authentic, they are generally pretty accurate on the grade, and are a good source of protection for the coins.
Cons include the inability to hold the coin in your hand or open the holder without breaking it, those often cost more, you're less likely to get a killer deal or bargain on graded coins since prices are more set.
My advice would be to hold off on buying anything until you learn more about the different aspects of coins and collecting in general.
It's a big, dangerous world out there filled with problem and altered coins, and sometimes counterfeits and to start buying without doing proper research would be a boneheaded mistake.