There is a Derbyan at both bird stores by me. They are an IRN relative, but bigger. Heavy chewers, individuals can be noisy and or loud, if tame can hang out with you like an IRN or Alexandrine which is another relative, but like them, don't enjoy body petting... Oh, but gorgeous eye candy though!
I think the ones I know of (who were/are for sale) are adults at the store was because they were very picky who handles them and would only be sweet to certain people, and try to take a chunk out of most of the customers. I will look at and talk to "Derby Girl", but I won't dare try to pick her up. I just love to stand by her and see her beautiful colors.