I simply go to my internet browser, (Google, Edge, Bing and others), and search NGC VERIFY or PCGS VERIFY, and that provides a link to the verification page on their websites, where you can simply type in the certification number, to make sure it matches the coin you are considering purchasing. Many grading companies even include photos of the coin, in its certified holder! Of course that may not help if the person selling the coin has altered the certification slab, but it is a good and free precaution to take before buying a coin, especially on the many auction sites out there where some people are simply taking crummy or even counterfeit coins and putting them in a plastic slab to make them appear to be certified coins! Its a pretty easy thing to do, to find a particular coin, copy the cetification number, and put it into a slab. If the number does not match the coin, or if the photo of the holder is different than the one for sale, then it is most definately a rip off. I apologize if this is old news for many of you fine folks. I hope that, at least, a few collectors or investors find this information useful. I was not aware of ths free service until a short time ago. HAPPY HUNTING & GOOD LUCK! I posted this as recently I viewed a 1972 DDO Cent. I checked the certification number and it looked fine, but one of the photos of the coin for sale was taken with the coin NOT in the holder. I asked the seller why he took the coin out of the holder, and he replied that he was a new collector, and did not have the money to have his coins graded.....YIKES! Big red flag there. I did not purchase the cent as it was obviously not what was advertised and the photos and certification number had likely been copied from one of the grading services websites. The second red flag on his listing was "Returns not accepted"!