3rd (or 3rd and 4th) digit

Racing Category

In Year

1

Formula 1

1970-1978, 1981-1982, 1987-1991

2

Hillclimb

1977

2

Formula Atlantic

1972

2

Formula 2

1970-1984

3

Formula 3

1969-1981

3

Formula Super Vee

1978

5

Formula B / Formula Atlantic

1970

5

Group 5, 2 Liters

1973-1974

5

Group 5, 2 Liters and 3 Liters

1976

5

Formula 5000

1972

7

CanAm Sports Racing

1970-1971, 1973, 1981-1982

8

Formula Ford 1600

1970-1971

8

Formula Ford 1600 (USA)

1972

9

Formula Ford 1600 (USA)

1970-1971

9

Formula Ford 1600

1972

2A

Formula 5000

1972

A

American Racing Series (Indy Light)

1986

A

Formula B

1979

A

Formula Atlantic/B

1980, 1982

A

Formula Atlantic/ Pacific

1979, 1981

A

Formula B (USA)

1981

A

Formula 5000

1972-1976

B

Formula 3000

1985-1990

B

Formula Atlantic/B

1971, 1973-1979

B

Formula B (USA)

1972

C

Formula 3

1979

C

Indianapolis

1980-1989

CE

Indianapolis (Alfa Romeo)

1989

CGxxx

Formula 1, dedicated to Cesare Gariboldi

1989-1991

G

Formula 1

1972

G

Group C and GTP (Grand Touring Prototype)

1982-1988

GC

Grand Champion (Japan)

1988-1989

H

Hillclimb

1977, 1981

J

Formula 2 (Japan)

1985-1988

N

Group C and GTP (Nissan)

1988

O

Oldsmobile Record Car

1985

P

Indianapolis (Porsche)

1989

P

Group 5, 2 Liters

1974

P

Formula 1 (Porsche)

1987

P

GTP (Grand Touring Prototype)

1981

R

Formula Renault

1975

S

Formula 2

1979

S

Sports 2000

1980-1984

S

Sports Racing

S

Group 5, 2 Liters

1973-1976

SV

Formula Super Vee

1979-1980

U

?

V

Formula Super Vee

1979-1980

X

Formula 1

1972

4th Digit

2

Group 5

1975

A

Formula 5000

1972

B

1971

B

Formula 1

1976

C

Formula 1

1976

G

Formula 1

1972

M

Monocoque

P

Formula 2

1977

P

Prototype

1971

S

Spaceframe

X

Formula 1

1972