This is a brand new wrench made exclusively for Rolls-Royce Silver Shadows and derivatives with hydraulic rear rams. Over time, these rams can be well and truly stuck, especially if there has ever been a brake fluid leak effectively rust-welding them in place.  This wrench allows tremendous force to be used to break these rams free. A cheater bar can be used over the handle if stupid-ridiculous force is needed.
The spring top that the rams are screwed into may turn with the rams as they are only held stationary by the weight of the car. These wrenches have notches in the sides to allow an air hammer to find purchase to drive the rams out without damaging the teeth. This wrench is cut with a CNC water-jet and fits the teeth on your rams precisely. It is best suited to unmolested rams. If the teeth on your rams have been previously mangled by a vandal with an air chisel, this wrench will not fit without considerable time spent in the boot with a Dremel tool and a file. You'll probably be time ahead vandalizing it further with an air chisel and fixing it later. BTW can provide new stainless ram pistons if worse comes to worst.
These wrenches are 10mm thick and are zinc plated.