Some say that it is somwhat crass to leave the bottom button unfastened. I wouldn't go that far, but I do believe that it is only necessary if the wearer of the coat thinks this is the only distinguishing mark of the coat itself and feels it should be exploited for others to see. If a coat is well made, well cut and from a good fabric, then leaving a cuff button unfastened, well, it speaks volumes. I have a client from West Virginia, I've been making his clothes since about 1969. He loves clothes as much as the members of this forum. He is height challenged, weight challenged, but extremely bright. he was, at one time, the youngest supreme court justice in the English speaking world (as the article I read once stated) His biggest problem was that he hailed from Charleston. So, he is staying at Claridges with his girlfriend from NY. they are invited to a dinner party by his his girlfriends ex boyfriend who, seing this height and weight challenged person with a funny accent, decides to have some fun with him. Eventually, after much verbal sparring, they get round to clothes. Seeing that Richard has all his cuff buttons buttoned he says to all around that it was plain his suits were superior because his bottom two holes were functional. At which time Richard responded that all four of his cuff holes are functional. Now, what this story proves, I don't know. but I think there's a little something there to think about.