Polish have the double horns on their combs as well.
Edited to say: I am really not sure there is a lot of difference between crevecoeur and Polish, not that I can see anyway.
Well, now just because it looks like one doesn't make it one. You really can breed a black Polish as well but I am not sure they would breed true (someone on ebay told me that they bred a golden Polish with some other color Polish and all the babies were black). I think you would have to hatch...