SECTION III: Weapons Removed From The NFA As Collector's Items And Classified As Curios Or Relics Under The GCA
The Bureau has determined that by reason of the date of their manufacture, value, design and other characteristics, the following firearms are primarily collector's items and are not likely to be used as weapons and, therefore, are excluded from the provisions of the National Firearms Act.
Further, the Bureau has determined that such firearms are also curios or relics as defined in 27 CFR 178.11. Thus, licensed collectors may acquire, hold or dispose to them as curios or relics subject to the provisions of 18 U.S.C. Chapter 44 and 27 CFR Part 178. They are still "firearms" as defined in 18 U.S.C. Chapter 44.
# Mauser, commercial Luger Artillery model semiautomatic pistols cal. 9mm, Mauser banner marked, produced under contract for the Royal Thai Police accompanied by original, German mfd., detachable wooden shoulder stocks.
# Mauser, model 1896 semiautomatic pistol accompanied by original German mfd. Detachable wooden
holster/shoulder stocks, all semiautomatic German mfd. variations produced prior to 1940, any caliber.
# Mauser, Pistol-Carbine, model 1896, 7.63mm, with shoulder stock and 11-3/4" to 16" barrel.
# Mauser, model 1902, 6 and 10 shot magazine capacity, semiautomatic pistols in cal. 7.63 x 25mm (.30 Mauser), having the distinctive hammer safety, barrel lengths of either 3.9 or 5.5", and accompanied by an original detachable wooden holster/shoulder stock.
# Mauser, model 1912/14 pistol, 9mm Mauser short or .45 ACP, with original detachable wooden holster/shoulder stock and 5" barrel.
http://www.atf.gov/firearms/curios/sec3.htm