This is the type of bonnet used on the TR4 Works Rally cars.
The early TR4 bonnet has a much shorter bulge and no accomodation at the back for cone shaped bonnet pins. The correct bonnet pins are flat topped, but provide no location. The bulge is approximately 2" shorter than subsequent bonnets. This bonnet was fitted up to CT6429. There was also an intermediate bonnet with long bulge and no rear location. The more usually known bonnet is the third type with the long bulge and location at the back for cone shaped bonnet pins.
These bonnets are supplied with additional strengthening to the rear where the original design is inherently weak.
Should you require an early bonnet, this must be specified as they are only made to special order.