Unless you've inherited your guns, or bought them more than 25-years ago, there is a very good chance that a database on them already exists somewhere. I know that there isn't supposed to be, but I'd be frankly shocked if there wasn't. And really, if there was ever a risk of some type of confiscation, don't you think we'd have plenty of other, far-bigger problems? With that said, the obvious upside of a database/archive would be valuation, pure and simple. You certainly wouldn't have every example logged-in, but you would have a fairly good idea about surviving numbers and the general rareity of a specific variant. Human nature being what it is, the accuracy of this would be more valid for the higher-grade guns.