Not sure if they all had, but mine does. It would be cool to try and replicate it, shouldn't be that hard to do.
Here's a little tip I have learned from building models: when I want to have that splattered mud look on a tank/vehicle/whatever, I dip my brush in the paint, get the excess off of it, then gently blow on the end of the brush and it applies the "splatter" effect to the model. Adjust the size and amount of splatter by adjusting the amount of paint on the brush.
Just make sure to practice on something else first....