1930 Alfa Romeo 6C 1750 4th Series Supercharged Gran Sport Spider 15 January 2019 1930 Alfa Romeo 6C 1750 4th Series Supercharged Gran Sport Spider Not sold. Highest bid €1,050,000 Estimate: € 1,200,000 – 1,600,000 Auction: Bonhams Paris 2019 © Courtesy of Bonhams