I also think it's chrome. You say "it shoots like a dream" so I'd leave it as it and enjoy it. From what I can see, the lines have been smoothed somewhat as it was no doubt polished before the chrome was applied and will never be original again.
As Don says, everyone should have a chrome or nickle plated Luger. Mine is an all matching alphabet commercial and, like your Artillery, it's a very reliable shooter.
Shoot it, have fun and enjoy the attention it gets at the range from envious people.
