Rust on flash suppressor? Brand new Daniel Defense upper

Hi guys. Just bought a brand new Daniel Defense upper. After the initial inspection, I found what looks like rust on the flash suppressor. I don't see any more anywhere else. Any chance this is something like cosmoline? I took an oiled qutip to it and some of it came off very dirty.

Guessing it's likely grease, since some solvent took it all off rather easy. I found some of the same looking stuff between the chamber and locking lugs that wiped right off. Any confirmation would be appreciated though.