Those of us with digital clock in our dash clusters (and that would most of us with Mk2 dashes) have the capability to have a 24 hour military time style readout. Some have it normally and would prefer the 12.
I think I've figured out how to change them.
The first pic shows the clock removed from the dash and the readout removed from the clock so only the circuit board remains. Looking VERY closely at the circuit board you'll see two solder pads with the labels 12H and 24H next to them. (shown here on the left)
The 12H pads on this one are shorted out by a circuit trace. The 24H is not. To change the clock from 12 to 24 simply cut the 12 hour trace where shown with an Exacto knife and solder across the 24 pads. If you wanted to get fancy you could solder in a switch to change back and forth.
I am still wondering why these cars have this option since I am not aware of any countries that use 24 hour time. However the popularity of VWs with the American military stationed in Germany might explain it. And many of those got shipped back home.