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You can usually tell the earlier Grey Market cars by the rust. The newer
cars, since 1981, are easy to identify by the VIN numbers.

The new numbering system is international and uses 17 digits
(123-456-78-9-10-11-12-13-14 15 16 17). The first three digits are the world
manufacturing code and Porsche's code is WPO. The next three digits (456)
are the VDS code for the U.S.A. and Canada. These three digits on the rest
of the World cars are ZZZ, so if your car or a car you are looking at for
prospective purchase has a ZZZ in this (4 5 and 6 digit position) the car is
a Grey Market 911.

The VDS code consists of two letters and one number. The first letter (digit
4) indicates which series car it is. The character A indicates the series is
911 coupe, the character E indicates Targa or Cabriolet and the character J
indicates Turbo Coupe.

The second letter (digit 5) indicates that the engine is for either Canada A
or U.S.A. B. The number in this sequence (digit 6) indicates the type of
restraint system; "O" stands for passive. These three digits are ZZZ for the
rest of the World cars and are considered as fill-in digits or specific
vehicle code for U.S.A. and Canada.

The next two digits (78) are the first two digits of the Porsche model type;
91 indicates 911, 93 indicates 930 and 95 indicates 959. The next digit (9)
is used as a test digit. The next digit (10) is a letter indicating the
model year, 1981 was the letter B and 1987 is the letter H.

The next digit (11) is a letter indicating the manufacturing location; S is
Stuttgart. The next digit (12) is the third digit of the Porsche model type;
1 indicates 911, 0 indicates 930 and 9 indicates 959. The next digit (13) is
the code for the body and engine. The remaining four digits (14 15 16 17)
are the sequential serial numbers: WPOAA910BS120001