The differences are small, silent, and completely visible once you know them. Five places to look.
Watch a man reach for a glass. On a hand-cut jacket the collar stays against his shirt through the whole gesture; on a factory jacket it lifts and gaps. The collar is sewn on by hand, curved to the neck it was measured against — it is the first thing a tailor looks at on a stranger.
Arms do not hang straight — they pitch slightly forward. A bespoke sleeve is set to your pitch, so the sleeve is clean when your arm is at rest. Ripples at the front or back of a sleeve are the sleeve arguing with the arm inside it.
A hand-padded lapel curves up from the button like something alive; a fused lapel is creased flat like a folded letter. Look at the lapel side-on. The roll is the visible signature of the canvas you cannot see.
On a striped or checked cloth, look where the sleeve meets the shoulder and where the pocket meets the body. Matching a pattern across those seams wastes cloth and takes time, which is exactly why it is done — or not done.
A hand-sewn buttonhole is dense, slightly irregular, finished with a knot of thread like a full stop. A machine's is flat and perfect and dead. The lapel buttonhole is the place every tailor checks another tailor.
None of this is decoration. Each sign marks a decision made against one man's body rather than a size chart — which is the whole argument for a bespoke suit, made visible.
The house will write to you to confirm the hour.