Jim,
Right on. I lost my standards in about 1983...
WPO: West germany, POrsche
ZZZ: digits for US/Japan markets
96: first two digits of car type (964)
Z: filler
P: Year of manufacture, 93
S: plant of build, Stuttgart
4: last digit of car type
1: body type (I'm lost here...)
XXXX: car sequential number.
GeorgeK