Identical Versus Fraternal

I have 2.5 week old twin girls, born at 35.6 weeks and amazingly healthy and big! My question is, when I was pregnant there was some debate as to whether they were fraternal or identical. My family doctor said they are fraternal because they are in two different sacs with two placentas, but from certain things I have read, this can still be identical if the egg split early on?? My girls look identical with the only real difference being that one is just slightly smaller (about 4 oz) than the other so her face is not quite as full. But, my husband and I have both mixed them up a few times leading me to paint pink nail polish on one's toe! What's the consensus...can they be identical or are they for sure fraternal?