A simple transposition of numbers? A poorly stamped number, so an 8 might look like a 3 or 6?
Curious indeed.
I wonder if somebody is importing counterfeit lowers from China, and even LE has them in inventory.
I wonder what that does to any legal case, if the prosecution says, the ballistics show that so and so shot so and so with rifle X at this time, and the defense shows rifle X cannot possibly exist as described in the report.