This is a common mis-conception by many, including dealers!
The serial number range you mention only mattered when the list was first developed! At that time, those would have been 50 years old (If memory serves, it was in about 1986 when the Curio and Relic FFL was first offered). As WHEELGUN states, if a gun is 50 years old as of today, it's a C&R. There are other catagories that are in the list that aren't 50 years old yet. These include some of the commemoratives, etc. that have more intrinsic value than shooter value. The list also contains some guns that would otherwise be class 3 short barreled rifles or shotguns, etc. that due to their value as a collectible, have been listed.
I've had to re-educate several field agents (with the help of ATF in Atlanta) who were passing on bad information about the way a C&R item is defined.