Formerly in London it was not permissible for a man to go to a luncheon or afternoon party in anything but a black tail-coat and striped trousers – the official morning-dress. Now he may go in a lounge-suit, but this should be of dark material or blue serge. Many men strike a happy mean by wearing a short black coat with striped trousers.
Book of Etiquette (1931)
It seems to me that the “happy mean” put forward by the British in the late 1920s remains a perfect compromise for North Americans today.
Here in Canada and the US morning dress has become virtually extinct and most grooms blithely don evening dress for formal daytime weddings. Other men who know better than to sport tuxedos in broad daylight are faced with the dilemma of choosing the correct but anachronistic daytime tailcoat (known here as a cutaway) or settling for the informal and relatively mundane dark suit. Very few are aware of the happy medium known as semi-formal morning dress which replaces the cutaway coat with a modern black or dark gray suit jacket while keeping the remaining elements of formal morning dress, mainly the coloured waistcoat and striped or checked trousers. The end result is an outfit much more modern than standard morning dress yet much more distinctive and traditional than a basic suit and tie.
Best of all, you can minimize your investment by borrowing the jacket from your existing dark gray or black suit (which, of course, you only wear to evening functions or funerals) as demonstrated by boulevardier AlanC in these photos.
Here’s a couple of examples of a more formal interpretation of the outfit using striped trousers and uncoloured waistcoats. Interestingly, the first example is marketed in the UK as a “masonic jacket”.