From the listing for this Classic Porsche 911 Race Car for sale:

One of only 54 genuine examples built by the Porsche factory racing department during 1974 and 1975 intended specifically for Group 4 motorsport purposes.

Chassis # 911 460 9074 was purchased new in partnership by Giorgio Schön and his friend and co-driver Giovanni Borri of Italy, for the 1974 World Manufacturers’ Championship.

The car was painted the night that it arrived from Stuttgart and raced the next day at Monza in practice for the 1000 kms, where it achieved fastest time in the GT Class.

Schön, the son of the famous 1950s and ‘60s Italian-born fashion designer, Mila Schön, had the car painted the night that it arrived from Stuttgart in a blue, light green and white Harper’s Bazaar livery, which was styled by his mother – the next day at Monza in practice for the 1000 kms, they achieved fastest time in the GT Class.

The car competed actively for three years. In 1975, the light green was changed to turquoise and it is extensively well-documented photographically in both liveries during the 1974, ‘75 and ‘76 racing seasons