you need to have and read the ATF Curio and Relics list which also lists the pistols/rifles exempted by specific types and/or numbers...the following is from pages 34-35
These are
"WEAPONS REMOVED FROM THE NFA
as collector's items and classified as curios or relics under the GCA"
Orv Reichert
http://boards.rennlist.com/upload/BATF.jpg