San Marino
In 1975 rumors were that the Skyhawk was scheduled to receive a companion model in the form of a Buick based on the Chevy Monza Towne Coupe. Harry Bradley worked on this artwork and came up with the Buick San Marino.  The San Marino name did no come from the tiny nation in Europe but from the city outside Los Angeles that, according to Guinness Book of World Records, has more millionaires per square mile than any other spot on earth.  One can see this luxury mini-car as a baby Riviera.  The article also states that Oldsmobile was also scheduled for a Towne Coupe based model, possibly the Oldsmobile Starfire Supreme?

As you can see by the watermark, this photo was taken, with permission, from Test Drive Junkie's website.  I have since found the article and the above photo in the August 1975 edition of Motor Trend magazine, pages 44-46 titled 'Preview: 1976 New Cars from GM'.