The speckled Sussex is really old, but I think the light came about later on. I read somewhere that Barred rocks were used in the original crosses but obviously some feather legged breed must have played a part. It's strange how little is known about the creation of many of our breeds and varieties but I find it interesting to learn as much as possible.From what I've read the Sussex as a breed is very old "one of the oldest British breeds". And the original Light Sussex birds were bred by crossing with Brahmas and Cochins. So I suppose that's why some slight leg feathering pops up sometimes.