The regulations used by the ACO were based on those of the new FIA, created in 1946. There were ten classes, based on engine size, and at least ten cars had to have been produced before the entry was submitted. Supercharged engines’ equivalence was calculated at 2:1 for engine capacity. However, for this new start, sportscar prototypes were now given admission for the first time, "as an exceptional measure to contribute towards a faster revival of automobile manufacture" by the French "Service des Mines" (Vehicle registration authority), or its foreign equivalent That was, in a sense, just formalising an unofficial practice started in the 1930s, when race-specific cars were entered at Le Mans and other races for the win with no intentions of going into full production. The ACO reserved the right to disqualify a car not entered 'in the spirit of the regulations'.