I just love Curbside Classics. They produce fascinating nuggets of US automotive history with a fond yet critical attitude. The comments are unusually good as well.
Further, they seem to have access to the catalogues of GM, Chrysler and Ford if the detail on the technical specifications are anything to by. This article deals with ten obscure special models. I notice that their use of the term applies to what I’d call trim variants that had their own badging and equipment. In Europe “special” seems to imply a plastic sticker and some cloth upholstery of questionable taste.
I notice that in the US trim designations had the habit of becoming standard models. Furthermore the designation could even become a model in its own right. The Cutlass name was once the top trim of the Olds F-85 and then went on to become a model in its own right. Then the name was attached to a variety of quite different vehicles. The 1959 Continental Mk IV´s top trim was the Town Car and this was true for the Mk V as well, referring to the highest interior trim option. In 1981 the Town Car became a stand alone model. I can´t think of an equivalent car from Europe. Can you?