The definition for curio or relic (“C & R”) firearms found in 27 C.F.R. § 478.11 does not specifically state that a firearm
must be in its original condition to be classified as a C&R firearm. However, ATF Ruling 85-10, which discusses the
importation of military C&R firearms, notes that they must be in original configuration and adds that a receiver is not a
C&R item. Combining this ruling and the definition of C&R firearms, the Firearms Technology Branch (FTB) has
concluded that a firearm must be in its original condition to be considered a C&R weapon.
It is also the opinion of FTB, however, that a minor change such as the addition of scope mounts,
non-original sights, or sling swivels would not remove a firearm from its original condition. Moreover, we have
determined that replacing particular firearms parts with new parts that are made to the original design would also be
acceptable—for example, replacing a cracked M1 Grand stock with a new wooden stock of the same design, but
replacing the original firearm stock with a plastic stock would change its classification as a C&R item.
If I renew a c&r after 16 months without having one, do I have to log the entire collection I acquired while unlicensed?
No, you technically did not or were not licensed in this 16 month time frame. You document those you acquire during your license period. You can add them in if you wish, just notate they were pre-license purchase.
Is it safe to assume anything 50+ years old is automatically c&R even if they are not included in the list?
I've wondered the same, because this is technically C&R
Now, the Marlin Model 99 pre-dates the Model 60, Model 99 Marlins were made 1959 through 1961. So technically this Marlin 99 would be in excess of 50 years old and is theoretically C&R.
As is this, my S&W Model 29-2 .44 Magnum, according to S&W, the serial dates it to 1963. It also is C&R according to the 50 year rule.