I'm surprised you rated the production so high. Most people seem to be in agreement that the production on this album is "tinny" and (putting it gently) could have been better. Production-wise, I find their other albums much more listenable.
I will be the first to admit that I am not really an audiophile or know a lot about production so maybe the complaints other people have had are warranted, I don't really know.
Why I rated production so high was because I listened to this after re-listening to The Moon is Down (maybe I shouldn't have done that, I don't know) and the production on The Moon is Down just makes everything seems reather dull. With Penny Black I felt that it just had such a fuller sound, which I appreciated a lot, so I gave it a good production score.