When you sell a unid anni, it doesn't matter what skin it has, a unid anni is a unid anni, it's the same thing you're trying to sell, if you have several different unid anni with different skins, you can always write them in the same topic, and if you have a topic up with 1 unid anni and you get one more, you have the option to edit your topic and write the new anni in your list, having several different topics up with different types of skins is against the rules