AR with strange lower...

Looks like its missing the "fence" around the mag catch button (ala old-school lowers), and has some stippling on the front of the magwell... what exactly do you think is weird about it? There are increasingly a greater variety of tiny variations here and there on the the lowers from different companies these days.

What is weird is that they have the rear sight mounted way forward on the rail, it looks like.

Pretty sure it's just the lighting that makes it look off. The fence is there; you just have to squint.

If it was a Magpul booth gun, I suspect that it was one of the fabled Magpul aluminum billet lowers.

That does appear to be an example of the elusive Magpul lower.

I don't see a trigger.
Could just be lighting/angle, but I can't see one all the same.

It's possible it's just a display piece and there is no trigger. I've seen other companies do that if they're just showing off accessories.

I think there's another company that makes a lower with a ridged, reinforced magwell/front takedown pin area. Sun Devil perhaps?

It is a Magpul lower with Magpul furniture.

If you look close it looks like there is a fence around the mag release.

Yup that's a Magpul lower.

Whatever it is, its kinda cool looking.

It is the Magpul Billet lower which as of yet has not been released.