Various Harmonic Balancers were used over the years. No clear information on what the differences are.

Model Years Part number Color Engine number  
928 1978-1979 928.102.120.14 black M28.01  
928 1979-1983 928.102.120.15 red M28.11/12  
S 1981-1983 928.102.120.16 blue/green M28.11/12  
928 1980-1983 928.102.120.17 grey M28.09/10  
S2 1984-1985 928.102.120.22 ? M28.21/22  
S2/S3/S4 1983-1989 928.102.120.23 orange M28.19/20 M28.43/44 M28.45/46 M28.41/42  
S4/GT 1990-1991 928.102.120.23 black/grey M28.42/47  
GTS 1992-1995 928.102.120.24 green M28.49/50  
           

 

This is the S4 vibration damper (GT/GTS are green). Notice the TDC marker and the -2 degree, -1, 0 +1 and +2 degrees mark

Damper with the Porkensioner fitted .... and what the damper should look like in your car.

This is what it looks like when the damper is placed reversed.