Alright, it looks like I did pretty well overall, thankfully. Bummer part first.
Since it had the full issue AR buttstock with storage well, the buffer tube is not inletted for an adjustable replacement. It looks like it was installed with no backplate, nor even a castle nut. The spring for the rear take down pin was protruding out, mashed into a perfect L-shape, and I couldn't see the detent pin on the front side. Okay, meh...not too much of a biggie.
Once I got the optic off, I could see that the front of the top rail was branded S&W just behind the Hexnut. So, upper and lower match. Got the handguards off, and turns out is has a nice barrel....
Faxon 16" Gunner Profile AR15 Barrel, 5.56 Nato, Pinned Gas Block - Faxon Firearms
I could see the bolt carrier was branded with an 'A'. Turns out it's this....
5.56 Bolt Carrier Group, Complete - Black Nitride | Aero Precision
Oh, and I had looked THROUGH the optic in the LGS, but not AT the optic. Found that it's this....
Nikon P-TACTICAL Riflescope .223 3X32 | 4.8 Star Rating Free Shipping over $49!
Thanks for the input, folks.