Long Key Short Key

Why there are two keys of different lengths that both appear to do the same job?

The long key is the Porsche Alarm key, the 'extra bit' goes into a switch which turns the immobiliser on and off, if you have the factory fitted immobiliser you will have the code 533 (Alarm system) on the options sticker in the rear, on the fuel tank, under the mat.

The actual 'lock' is the same, just has the additional electrical switch part and they are not interchangeable, and the original alarm may have been removed/disabled - Andrew Cowton '84 928S2 Auto Melbourne