I've purchased many coins on
ebay over the years (just about all of them graded
Morgan dollars and interesting silver issues) and, if I remember correctly, only two issues with sellers. One was the wrong coin shipped and the other had a cracked slab. Both were returned and money refunded without a problem.
I buy new
ASE issues direct from the Mint eliminating the middleman completely. You should have started there before yesterday and the end of sales. I usually have the best of my purchases graded and have become pretty good at determining which has the POSSIBILITY of getting the 70 grade.
I have also sold MANY, MANY coins on
ebay and, while not a dealer by definition, still sell near 5 figures worth every year. I have had to refund only one purchase when the buyer decided he overpaid for an item (he did...

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I noticed you are looking at a NGC69 SF set. Nice set and in that grade $167 is at the top range of prices. You can probably do better by trolling the auctions and getting single coins (with matching labels) to make your set (or finding a set at or around $150 shipped). I sold two of those sets this year. BUT...you have to decide if you are going to go at this willy nilly or have a plan...
I would suggest getting a set of burnished W's first..one by one...graded or not and THEN move on to the special sets.
That said, it's great to go to a coin dealer if you can find a reasonable one. The ones I visited didn't seem to care whether I bought anything or not and were not warm fuzzy people and had little interest in "modern crap"
There are also MANY reputable online dealers out there that submit coins in bulk and sell graded specimens at a reasonable price and before the 3rd party local dealer markup.
Yes, this is all in reference to slabbed items which, I think, is the safest way to insure what you see is what you get and the easiest to sell because they are a known grade and value is defined. Can some proofs develop spots? Absolutely...but there are some ungraded coins out there with occult issues also..
As was mentioned look at pictures, look at feedback, use a reputable seller (or dealer)
and do your research to get the present price range. It can be fun and you will miss some auctions because of underbidding...but better than getting the coin because of overbidding. There WILL be another for sale and the game continues.
Bullion, burnished, proof, reverse proof, enhanced finish, S, W mints, OGP or not, slabbed (69 or 70 grade, PCGS or NGC) or just plain raw. A lot to explore....
I will shut up now (I never should respond right after my morning coffee

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