It looks like a 1974-1976 generation Buick Riviera to me.
Yes, I knew it was a full size GM, but that long flat nose reminds me of thse old Rivieras.
74-76 Plymouth Fury…
Not Pontiac nor Cordoba are you. You are a 1974 Caprice Coupe!
Well, not quite, but it sure looks GM in front, rather than Ford or Chrysler…???
Front end is identical to this 1975 Mercury Marquis. Wraparound turn signal with chrome trim, the chrome strip that runs just above the wheel well and stops just short of the turn signal, chrome trim around the wheel well, wraparound bumper, chromed side mirrors. That’s all identical. The pillar/roof is different, though.
No. Check the front side lamps. There is no front fascia covering the lamps. Also, the side trim is not the same. The LTD has a longer front door than the mystery car, and it would have had landau bars between the two windows. The 70s Fury’s did not have front side lamps at all. I still think it is a Riviera. But I’m not entirely convinced. The windows look right, but the side trim is slightly different and the Riviera’s front side lamps are not all yellow.
I’m starting to feel better. I’m usually pretty good at identifying cars, but the disagreement here tells me my confusion is not abnormal 
I’m almost wondering if someone didn’t customize that landau top. It’s that mile-wide B-pillar that makes it so hard to match to any other car. And there’s something written in what looks like cursive in silver at the bottom of the B-pillar (just looks like a shadow in this pic, but we blew it up and enhanced it at the office yesterday). Couldn’t tell what it said, but it looked like two words. I was almost thinking “Signature Edition,” like on Lincolns, but that roofline doesn’t look right for that.