Glad you are joining the project!
Because of the Ship of Theseus issue I can’t print extra labels – it’s an interesting thought experiment with a good article on Wikipedia. It wouldn’t be a good idea to put the same serial on two cases, nor can I put a different label on just the case as it’s not a full keyboard – I had to think about this for a while. A bunch of folks have ordered extra cases and they sometimes indicate a preference for which case the label should be applied to. If you have two keyboards with identical serials and you add a separate inner assembly to the spare keyboard while there’s still one in the original case, then you’d have two with the same serial. Which is the “real” one – hence the Ship of Theseus concept. And a case alone is not a keyboard so it’s not eligible for a serial. That was my thinking at least.