Hmm....I have a pure white Icelandic hen that comes indirectly from the Behl line. The breeder I got my little flock from has been raising them for 9 years and he had told me that the white didn't show up in his flock right away. He only raises Icelandics, so I don't think there was any whoops. I love my little Svana. So there is always the possibility of a one color Icelandic, but if yours is laying a larger egg, you are probably right about her parentage.I have a confession to make. One of the chicks that hatched in December who's daddy is Drekki II came out of a LEGHORN egg and not an Icelandic. I don't know how I didn't notice it when I sent them to be incubated, but before I rehomed my flock to the FFA group in the East Valley and knowing that there is NO SUCH thing as a ONE COLOR Icelandic, I realized my Leghorn looking pullet with the 'interesting' comb had to have come from the two of them. (Her mama was hatched from a Trader Joe's egg) So I decided to keep her for life as a remembrance of my life with Icelandics... she just started laying and the egg looks like a cross between a leghorn and an Icelandic. Maybe I could call her "Stella II", but I can say she hasn't found her way out of the run yet!