I think it has to do with what their pattern is based on. For instance, sebrights and wyandottes have different chick down, but are both single laced as adults. That’s because sebrights are based on birchen and wyandottes are based on partridge or columbian (I’m not sure which).Doesn't look like a Speckled Sussex chick but does look very similar to a Jubilee Orpington chick and they grow up to have quite similar appearances. A bit off topic but @RoostersAreAwesome, do you have any ideas as to why the chick down differs between breeds? I was trying to dig into it more and I think I'm finding conflicting information. I was reading that Speckled Sussex have a different genetic background in the US versus other countries and when I was looking, it even appears that Speckled Sussex chicks look quite similar to this chick overseas... OP, what country are you from?