Well, nobody can say with certainty that a coin is genuine just by looking at it. So even if you took them to a dealer he would have to at least weigh them to see if they were genuine so you may as well do it yourself. Besides, even if you did damage them somehow it would not affect their value since they are just bullion coins. But say you did, you could always sell them and just buy more.
Actually some bullion coins such as these sell for above spot,(provided there is no noticeable damage) depending on the coin, but You`re right in regards to the fact that even with damage, they will always be worth at least spot. : )
But only very, very few of them. And then to an even smaller group of people who seem willing to pay that premium mainly because they don't realize that nobody else in the marketplace will pay the premium.