[Vwdiesel] Early Fuel Pump

[Rudy]

I recently picked up a 1980 Rabbit, the specs in the Bentley Manual specify
two different Pumps and different Timing specs for each.  There are a couple
yellow paint marks on a couple different Bolts on this pump but they are
similar to the marks put on by rebuilders who have done pumps for me
recently.
 
Anyone know how to identify the Yellow Dot and non Yellow Dot Pumps?  The
differences in the Timing specs are considerable.  
 
Rudy