Hi Don,
The 3:1 tacho for the late A10 models also has the letter "L" which means it has the opposite rotation to "normal"
An extra gear is fitted between the cable input spindle and the chronometric mechanism to correct the rotation for the
dial, then it has to be recalibrated to the different ratio.
In reality it is not a home job, unlesss you have accesss to a stash of spares etc
Most good repairers would either convert your tacho or trade yours against the correct one
HTH
John