I noticed mine has this too - I like it, I think it may also prevent spit up off of the coils? Got my 3rd coil on and I think I finally have the hang of it. It's right at 3 ohms, and seems to be staying there. I think it's starting to get "seasoned" as the flavor is getting better and better.
Clyde - one thing I haven't been able to do is put it on my P+650 without an extender, are you able to use it without an extender? I really hate to use adapters and extenders with the rhodium contacts, if I don't have to.