Re: returning it...
I was satisfied with the machine, the usage was trivial and did not distress me; and I needed it immediately. Had the situation been more flagrant or extensive, I'd have chucked it back at them. I'm not easy on such things, but this unit was already overdue for use in the project for which I'd bought it, I had numerous replacement components (RAM and drive) installed before I found the signs of previous use, and so, uncharacteristically, I just shrugged and passed it off as an annoyance. Grrrr to dealer, purrr to machine. It cancelled out.
FYI, I will probably ask the moderater to zap my posting that specifically mentioned MacMall. I'm not much of a fan of them, and I do most of my third-party buying with Amazon or Micro Center; I'm aware of MacMall's years-long "history" of problematic behavior on sales and refunds; still, I'll cut 'em slack on this one since I can't be absolutely certain what happened and there was certainly no indication that it had had any "retail" use or was a returned unit. Perhaps an employee just fiddling around a bit. You're welcome to offer thoughts on that.
Sorry for my lack of clarity on the other issue. I meant to say that, when booted from the USB3 jump drive, the "ignore ownership" checkbox was ticked on the MacHD in its Get Info. Not sure how that plays with the utilities and System recognition of ownership of files on the MacHD, or if it only applies to usage or access to those files by someone looking at the MacHD as a user or admin of, and when booted from, another boot drive (hope that speculation is clearly stated). I mentioned it just to cover the possibilities.
Thanks for your insightful guidance on this matter. When the backup is completed, I'll follow your (very clear!) instructions and move forward. I'll give you a progress report.
SJ / Houston
FYI - particularly puzzled about the aspect of this problem that, after the problem rears its head, allows me to nevertheless open and use the files IF I log out and log back in. Interesting. Anyplace you'd like to point me so I can read up and learn a little about the handling of permissions in this kind of situation? Curiosity. Tnx...