You can definitely tell the difference just by looking between a 4 degree retarded crank gear and a straight up crank gear. The straight up crank gear will have the keyway and the dot punch lined up. The 4 degree retarded crank gear has the dot punched to the left of the keyway. Here is a picture of the difference between the early straight up crank gear and the 72+ 4 degree retard crank gear (courtesy of FTE member Frankenstang57)

The gear on the left is a pre 72 straight up crank gear and the gear on the right is a 72+ retarded crank gear



Cheers,

Steve