Buttonable, though never unbuttoned, coat sleeves
There are two kinds of men. Gentlemen whose cuff buttons unfasten. And men whose do not.
A Gentleman does not advertise the fact. Parading round with cuff buttons unfastened is worse than having fake buttonholes.
A Gentleman would sooner walk round with his fly undone than his jacket cuffs.
This is not an arbitrary rule.
Nor is it difficult to remember.
It is simply known.