The studs along the frame of this chair are set by eye, not by a jig - and there is a reason for the extra work.
A stud line follows the outline of the frame, and that outline is full of changes: it swells over the arm scrolls, tightens under the crest, straightens along the seat rail. Space the studs at a constant pitch and they crowd on the tight curves and stretch on the straights, which reads as carelessness even to someone who could not say why.
So our upholsterers set the pitch slightly closer where the curve is tightest and slightly wider on the straight runs, so the studs appear evenly spaced to the eye as it travels around the chair. Each is then set to the same depth, because a stud driven a fraction proud catches light differently and shows as a bright spot in the line.
The line is also planned to start and end at a meeting point - under an arm scroll, where the eye does not look for a beginning. A stud line that visibly starts somewhere always looks as though it ran out.