Can anyone identify this?!

[kayooh]

I have come across a few 600 SEL cars in which one, two and as in this picture three of the intake tubes have daps of black paint!!
I did not make a mental note of any correlation between the number of paint daps and anything else related to the cars.
I don't know if anybody else shares this with me, but occurrences such as these make me spend endless hours wondering why and how.
Could it be a MB mechanic's ritual or something similar??