It was acrylic lacquer. The AMA specs only says "acrylic lacquer". The '68 Sales Manual describes it as; " 'Pontiac's 'Magic Mirror' finish is achieved by a special Thermal reflow painting process, using acrylic lacquers. The result of baking the paint at an extra high temperature, just long enough for the paint to reflow, is an exceptionally smooth surface that retains its 'showroom-new' look far longer than ordinary finishes."

For originality, I used acrylic lacquer to refinish mine years ago. Heating my garage to "an extra high temperature" was not an option so I had to do a lot of buffing to get the look I wanted.