Interesting case on evidence under the NFA
Text here. A 1982 ruling. At trial, the prosecution got admitted into evidence a certificate from the NFA branch records custodian to the effect that the possessor of the NFA arm had never tried to register it, had never paid the $200 tax, and that the firearm had never been registered. The court rules that the certificate could be used to establish the last, that it had never been registered, but was hearsay at to the first two. The NFA records (the only ones of which the person signing the certificate was custodian) would not reflect whether the transfer had been applied for, and the tax stamp was issued by the IRS, not the BATF.