A better analogy would be traces. They're almost never even theoretically useful, because they terminate with the being gun stolen or sold in a way that can't

A better analogy would be traces. They're almost never even theoretically useful, because they terminate with the being gun stolen or sold in a way that can't be traced, but they start with asking the manufacturer which distributor bought the gun, which leads to the gun store, where the ATF Form 4473 tells you who bought it at the retail level. If manufacturers forced distributors and gun stores to sign NDAs ... well, we know how that vs. the clear laws and regulations on the books would resolve. Somehow these other Constitutionally enumerated rights seem to be getting about as much respect as the 2nd Amendment does....