A pic of the backs would be helpful. Also, if the backs are plastic, unscrew one and take a look at it for a part number, as virtually all molded plastic parts of that era had one. Ford part numbers are obvious, usually something like D3AB-******X-A or something like that, Mopar ones will have the pentastar logo on them somewhere, and a straight up 7 or 8 digit number without any letters is most likely GM. I'm guessing 70's, black vinyl went out of style by the mid-late 70's and high-backs became popular in the early 70s, so they're somewhere in that period.
late 70,s chevelle seats Pontiac ran the other direction and olds ,I dont know what they were thinking,,,but the pattern is ugly and definately not buick
I think they are 1974-77 or so Chevelle or A Body bucket seats...definitely not pre '74 with that shape backrest..