I almost got locked up because a certain Clayton county police officer did not even know what he was looking at . Thankfully a other officer showed up and actually knew about the class 3 process.
Technically speaking the only people with the authority to even ask you for your stamp is the ATF. You do not have to show local law enforcement your stamp. That said, it would probably be much better to just show them and go about your business.

Christmas came early!