When the Classic Mini joined the automotive world with the switch to fuel injection,  one of the main changes was computer control of ignition and timing.  This sensor mounts to the flywheel housing where it can "read" the position of the crankshaft from a reluctor wheel built into the back plate of the Verto flywheel.   This means that these models have a specific flywheel housing that provides a mounting location for this sensor.   The SPI models through 1996 for most of the world still retained a "distributor" although it has no advance mechanism and it's really just a cap and rotor to deliver the spark to the plugs.  By 1997, The MPI models (again for most of the world) did away with the distributor altogether, but still used this sensor with a more sophisticated computer to control a more modern coil-pack ignition system.

Here is the specific flywheel housing used with this sensor:

http://www.minimania.com/part/TRD10013/Flywheel-Housing