Go to the ATF web site. They have the info you need. sorry I do not remember what is, just do a search. From the material I have read, there is no class III license per say, except if you are a dealer. If you want to buy one, find a dealer, fill out the paper work and pay for the item you want to buy. They keep the item while your paper work goes through and at some point you have to get a signature from your local sheriff. The bad part is the wait. I heard of some guys waiting as much as 9 months to a year for the paper work to clear. Hope this helps.

Yes
But you have to become a C3 or a C7.
A machine gun dealer or manufacturer.

Which brings me back to my last post on this subject.

Are you looking for a brake, a flash suppressor or sound suppressor?

Each has benifits and liabilities.