We've had limited dealings with this company on ebay. The raw coins they sell are guaranteed "authentic", but that's it. They do not guarantee that they haven't been altered. Both my wife and I have sent them emails inquiring about this, and none of our emails have ever been returned. We were interested in buying their coins, but had concerns that the coins could have been cleaned etc. We also expressed concern that their photos in some cases make their coins appear too good to be true. Many photos of especially the raw coins do look enhanced–and there is no guarantee that the coin is original!
It is now 2016. I have purchased about a dozen raw coins from GSC and have had them professionally graded. So far, not one has been graded the way GSC graded it. Many aren't even close. I know they have 'experts' on board, but where are they? For example, I bought a 'Gem BU Red" 1909 VDB Lincoln. I expected it to grade out at about MS65 Red. NGC graded it 'Unc details, altered color'. Not good. A 1944 'Lustrous Gem BU Blazer' Walker came back AU58 from NGC. An 1897 S Morgan billed as a 'Gem BU++' coin came back only MS62, a far cry from MS65 or better. It boggles my mind that buyers are buying their raw coins, and in some cases are spending several thousand dollars, and are simply accepting GSC's grading opinion. These same folks leave glowing feedback without getting those coins graded first! Many perhaps don't get their coins graded at all. And many now own altered or overgraded coins–and are utterly clueless.