I just had an ATF inspection and the agent stated that pre 1899 guns do not need to go into the record book...AS LONG AS...they have not been altered, such as new wood, finish, etc. YMMV.
This is proof that even some BATF Agents do not understand the law. The law is the law. It is passed by Congress, and signed into law by the President. The law is printed word for word in the Congressional Record. Terms such as "Antique Firearm" are specifically defined. You will not find anyplace within the law that states what this misinformed agent told you.
But if this was indeed true, it would certainly add great importance to maintaining and confirming original finish... as if that would even be possible.
By the way, did this agent happen to photograph your Bound Ledger Books while he was conducting his inspection? I'm just curious about how prevalent that particular illegal behavior might be.