Coachbuilding, in which a body is made individually rather than pressed in volume, was standard practice for decades and then nearly vanished. Its recent return works differently from the original.
Separate chassis made the original practice possible
Early cars were sold as a running chassis with engine, transmission and suspension, and the customer commissioned a body from a separate firm.
Because the structure was in the chassis, a coachbuilder could design almost any body without affecting how the car held together.
This produced enormous variety, with the same mechanical package appearing as a limousine, a sporting two-seater or a delivery vehicle.
Unitary construction removed the opportunity
Monocoque bodies combine structure and skin, so the outer panels carry load and the body cannot be altered without affecting stiffness and crash behaviour.
Manufacturing shifted to large presses and tooling with very high fixed costs, which only make sense across substantial production volumes.
Coachbuilding survived only in niches such as hearses and armoured vehicles, where the work is engineered as a conversion with its own approval process.
Modern rules changed what is permitted
Crash performance, pedestrian protection and emissions certification are validated on a complete vehicle, not on a chassis, which makes independent bodywork legally difficult.
Small-series and individual-vehicle approval routes exist in most markets, but the testing burden is significant and varies considerably by jurisdiction.
This is why contemporary coachbuilt cars are almost always produced by the original manufacturer or under its direct supervision rather than independently.
Approval also expires in a practical sense, because a body altered after certification can require the whole vehicle to be retested rather than only the modified section. That cost falls across a run of a handful of cars, which is why the work is now scheduled alongside a model's original development.
Composites replaced the panel beater's craft
Hand-formed aluminium over a wooden buck has largely given way to carbon composite panels made in moulds produced from digital models.
Tooling for composites costs far less than steel press tooling, which makes a run of a few dozen cars viable where a pressed body would not be.
The underlying structure remains the donor car's, with the new bodywork attached to hard points designed for it, preserving the certified crash structure.
Why manufacturers revived it
A coachbuilt model demonstrates capability and generates attention out of proportion to the number produced, which has value across the whole range.
It also serves customers who already own everything in the catalogue, offering exclusivity that a specification sheet cannot.
The economics work because these cars command prices well above the donor model, covering the design and approval work across a very small run.