To get back to your original question, most of the hatcheries that market their Red Sex Links under the label, Golden Comet, cross a Production Red rooster with a Rhode Island White hen. One exception is Hubbard's Golden Comet which is a New Hampshire rooster X a White Rock hen. However, as has been pointed out earlier in this thread, you can produce a Red Sex Link by crossing any red gene rooster (RIR, NHR, Production Red) with any white/silver gene hen (White Rock, Rhode Island White, Delaware, Light Sussex, etc.) and no matter which of these you use the newly hatched male chicks will be whitish and the females will be reddish, and they will all be egg laying machines. Or if you want a Black Sex Link, you can cross a red gene rooster with a barred gene hen (usually Barred Rock, but could also be Dominique, or Cuckoo Marans) and the male chicks will be black with a white spot on top of their heads and the female chicks will be solid black; and like the Red Sex Links, the Black Sex Links will be egg laying machines.