This is an addendum to The Waistcoat Theory, that personal hobbyhorse of mine that attempts to solve the problem of men taking their suit jackets off indoors, and undermining all the aesthetic advantages of a suit as a result. I won’t repeat the details here; a quick search on this site for those words will produce more information on the subject than you could possibly want.
But in brief, the answer is the waistcoat – matching the trousers, worn with a tie and covered by whatever coat is required for the weather outside (topcoat, blazer, nothing at all).
The point was made to me recently, however, that a normal waistcoat could do with some improvements in this mould.
For a start, men can feel a little self-conscious these days wearing an item with a back made of silk. The shiny lustre this displays, together with the silk tie that is normally included across the waist (though this should be purely decorative if the waistcoat fits well) gives a slightly effeminate or ornamental look. Indeed, that is one of the reasons a waistcoat often reminds one of a wedding.
Of course, this silk backing would traditionally never have been seen. Like the lining of the jacket, and of the sleeve, it is purely to allow easy wearing and removal. As the jacket would not be removed, this lining would not be seen.
Secondly, the waistcoat could do with one or two aspects of the jacket to make it feel more formal and suited to be worn on its own as a replacement for the jacket. Primarily, it could do with a collar.
While waistcoats come with many different types of collar (notch, peak, shawl), the notch collar and lapel will look the most natural on a two-piece suit of the type we are discussing. Small peaks on a waistcoat will everywhere look odd, and a shawl collar suggests something too dressy.
Most waistcoats had collars when they were first made, so this is a return to the traditional form. The main reason for their disappearance over the years is money: more material, higher costs.
The replacement of the silk back with self (the same wool as the front) is also traditional. All tailored waistcoats descend from the original postboy vest of nineteenth century England, which was worn for warmth while driving the horses of a coach. As it was worn on its own, largely for warmth, it had wool both front and back.
Obviously having a waistcoat after this fashion requires a tailor or some means of having items made to measure. But then, that should always be the case with waistcoats.