AT ART-9 vs Audio Note IQ3

Probably you are hearing the mounting hardware (tiny nuts and bolts) rattling around in their container, but I wouldn't say for sure.

The notion, promoted apparently by AT, that the ART7 is "more for classical music" (compared to the ART9) is a bunch of hooey.  I own an ART7, and I play jazz and R&B nearly 100%, to my great pleasure with the ART7.

ART9 is the better cartridge IMO. Good choice.

I opened the box and unfortunately the cartridge was no longer attached to the headshell mount and was rolling around inside the plastic case. The cantilever cover was still in place and the cantilever is straight, but doesn’t it seem like not a great idea to keep a cartridge that was rattling around for 4000 miles? The sharp edges of the cartridge body put hundreds of tiny nicks all over the inside of the case.

That bites. What to do?

If there's no cosmetic damage, install and play it. If it sounds good, then nothing to worry about.