Do not get Jet Black!
Since 3Dmark performance / benchmark testing would make the device run hot, I removed it from the case. It's the first time I've removed it from the case since I opened the brand-new phone around 9/27 or 9/28.
That's when I noticed the speckles. They don't wipe off!
The Incipio NGP case had no particles or contaminants:
There are no speckles near the other cutouts at the bottom. [actually , there are] I just have no idea where this came from.
I only chose the Jet Black color because I speculated it would have greater resale value in 1y if I kept everything in perfect condition. That worked out well for me previously. I got my Rose Gold 6s Plus last year at launch and sold for $660 more than a week after the new phone launched. Looks like that's not going to happen with this one.
I will return it and get a regular flat/matte black instead. well I guess not since the return period is 14 days and this was purchased on 9/25.