There are millions of coins with dents, especially circulated ones. There are very few with "strike-through" errors, which is what this would have to be -- where a bit of hard material got stuck between the planchet and die while the coin was being struck. Even if this were a strike-through, at this point it looks like damage, and there's no way to prove it's anything else. The good news, if you can call it that, is that it doesn't hurt this coin's value -- it's still worth silver melt value, whether damaged or not.
If this was an error there would be a million people taking a hammer and a nail to the sun in their Walking Liberty Halves. You could look at millions of coins and never find an error. But most likely you will find a few that are minor errors.
Yep. If they were common and easy to find, they wouldn't be valuable. (Regardless of what YouTubers would like you to believe...)
