In any case, maybe I am misunderstanding what you mean by a 2-1/2. Would you care to explain?
On a true 3-button coat, the lapel roll ends just above the top button. Â The lapels are therefore quite short. Â Even if you don't button the top button, the coat will look "closed" pretty much all the way up to the top button. On a 2-button coat with an extra button, the lapel roll ends above the waist button. Â The extra "idle" button remains hidden behind the rolled lapel; on the other side, you can see maybe half of the extra buttonhole. On both of the above types of coat, the lapel roll ends in a pretty decisive fashion. Â The lapel should not look "folded over" in the sense of pressed flat, but there should be a clear point where it ends. On a 2 1/2 or "roll through" coat, the lapel roll does not so much "end" as just sort of "disipate." Â Rather than looking "folded over" right above the waist button, the lapel edge almost stands straight out. Â The lapel roll is much more gradual; the line of the lapel is longer than on a true 3-button, but somewhat shorter than a 2-button. Â You can see the upper idle button and buttonhole pretty clearly. Â Also, the coat above the waist button is open enough that trying to button the top button would really pull and strain the chest. This picture of a Castangia suit, worn by Renault78law, is a textbook example: http://www.styleforum.net/cgi-bin....lt78law
I am curious to know whether the Paul Stuart suit I have falls under that category, as it works buttoned to the top or the middle button only.
Strictly speaking, if you can easily button the top button without causing the chest to pull, it is not a "2 1/2".