No reason for it to be on the dealer invoice as it was not an extra. That's not to say it didn't appear on some, just as Norwood like to include extras on the cowl plate while VN did not. If you can find the build sheet, it will give more of an indication, as well as colour etc, even mostly standard for many paints. The opposite could also be true, if the bird was deleted and perhaps a refund of the feature noted. But when it was standard it was generally accepted as part of the WS4 package.