Switzerland seems to have this one nailed. Both parties are required by law to have documentation of a firearm sale, and that documentation must be retained for

Switzerland seems to have this one nailed. Both parties are required by law to have documentation of a firearm sale, and that documentation must be retained for ten years. If you don't have control of the weapon and you don't have documentation then you're in trouble. And I suspect you insurance won't cover any costs if you're in violation of the law.