Well, Even if they were the same whistle, they all sound different today...
844's is medium deep and rich
3985's is deep and rich, a little barky though
and the Big Boy one on 844 now has a deep, low, rich sound to it.
IDK if this is from age, use, or if they have been modified, but they all have a dferent sound.
This is easy to tell from youtube videos.