SOT= Special Occupational Tax
And there are
Three classes
The classes of SOT holders:
Class
1 - importer of NFA firearms
2 - manufacturer of NFA firearms
3 - dealer in NFA firearms
After the GCA of 86 went into effect, it banned further mfg for civilian consumption of machine guns. Hence the there are terms like Pre May DS Sample, Post Sample, and Pre 86. A civilian can only buy pre 86 stuff!