That's definitely NOT an NOS carb. It definitely has the wrong air horn, the plating on the small parts is wrong, the washers under the air horn screws were never there, the cover over the vent wasn't there, etc. That means the thing is probably hacked on the inside, too. It looks like a Q-power special, or a USA carbs part. Definitely, absolutely not an NOS carb.
Choke flap is wrong, but the bowl vent cover is correct...I have 3 of them with this cover in place. Some of the screws had washers, but originally they were not on carbs of this early vintage. It's definitely been rebuilt, so it's not a NOS....somebody shelled out way too much for it in any case.
The whole air horn is wrong, Len. You can't mount the special Star Wars bracket that protects the choke rod on that air horn w/o modifying it. I think the cover may have been a recall deal. I did not think they had them, especially the early ones. I have a pic here someplace of an early car with the air cleaner off from a magazine article, I think. The washers weren't used 'til way later maybe 74 or so. You see them on all the carbs, because the re-builders put them there. In the old days, we would just tighten them every now and then. I'm not a carb expert, but I've seen a lot of NOS carbs, and I was working on them in the 60's and 70's. But...yeah...somebody overpaid for it. That seller knows Buick parts, too. He knew it wasn't the right pull off, so I'm sure he knows it's not NOS. Caveat emptor I guess.
Thanks for posting that info, Frank and Len. I was very skeptical abut it being nos because I never saw a new Rochester carb without any finish coloring (gold). Also, the casting surface has some rough spots and the front brass plug appears to have created a hairline crack in the bore flange. I have a nos 800 cfm carb from a different vintage and the whole thing has a different look to it. I plan on posting some pictures of my carb sometime soon. It's never been unwrapped.