Cav Arms. And yes that was a retarded case
But if memory serves they also sat on his inventory for something like a year with no charges. And the charges that were filed weren't much of anything IRRC. I don't have time to do the research ATM
Cav Arms has had some fun in the last decade...
Under Warren Mee's ownership, got spanked by the feds. Mostly because Mee got snagged for some sort of real estate fraud.
With Mee in PMITA fed prison, Cav Arms continues onwards. They get nipped for "manufacturing violations" when an agent determines that if the plastics outsourcing firm they use has 2 halves of a receiver and some duct tape, you can make a half work on its own without a serial number. Manufacturing off premises. (I would argue that the seaming technique they use constitutes at least 20% of the construction process, making two halves combined still less than 80% of a receiver).
Feds didn't like Cav Arms because it was proof that the AR didn't need to be made out of metal, and inspired all sorts of inventive hillbilly AR's with no serial numbers. They hate the modular notion of the AR and that the serialed component is so easily made in a home workshop.