When Audi brought an Auto Union C-type and D-type to the VSCC's Richard Seaman Memorial Trophies meeting at Donington Park in May 2001 they also brought along other vehicles that are now under Audi's wing, including the one shown below.
This is a 1½ litre supercharged 60hp 1926 Grand Prix car, the NSU 6/60. NSU Motorenwerke produced cars from 1905 to 1969 when the costs of developing the rotary Wankel engine for the NSU Ro 80 crippled the small firm, and it was taken over by Volkswagen which merged NSU with the Audi brand that it had acquired earlier. I can't find out much about the NSU 6/60, except a comment on another website that says:
'During the years 1923-27 the NSU car racing era was at its peak, and several Grand Prix victories were a fact.'
The only records I can find for Grand Prix racing in the 1920s don't show any victories by NSU, and in fact the only race I can find in which the NSU's took part was the 1926 German Grand Prix, when the highest place NSU finished in 5th place, winning the 1½ litre class.
Here's the car at Coppice Corner during a demonstration run.