Selling "muzzle breaks" or something.....
http://www.wfmj.com/story/32807776/atf-arrests-east-palestine-man-with-nearly-200-firearm-silencers
An affidavit filed by an agent from the Bureau of Alcohol, Tobacco, Firearms and Explosives says that See told investigators that he has been making the devices for more than a year, then selling them on eBay for $50 to $80 apiece.
Although See calls the devices “muzzle breaks”, the ATF classifies them as unregistered silencers, bearing no serial numbers.
http://www.wfmj.com/story/32807776/atf-arrests-east-palestine-man-with-nearly-200-firearm-silencers