This was the heart of my question. On HTC's website it lists the ONE, it does not give different models it just gives all the radios and frequencies (it does say which radios work for which carriers) but does not specify that the phone does not include all of the radios listed only using the appropriate one for whatever network.
My Moto HD lists radios that work on both ATT and TMobile - including LTE bands that should work on either, yet the phone was an ATT exclusive.
My only question here was is there ONE version of the ONE or many. Looks like I am to assume many.
That said the deal being offered to me was a guy got an HTC One from his employer but preferred to keep his Iphone, so he was making a few bucks. Nothing shady about it.