Carbine Buffer Springs.

I have a couple of carbine buffer springs, and one of them is marked with green paint (?) on the coils.
Is this an identifier for something ? Or just a manufacturer thing to identify it as theirs ? Any information would be helpful.

Thanks,

SSB. [Tooth]

Wow, lots of good responses so far.

Are you sure you didn't just sneeze on all your buffer springs? [Tooth]