It is very likely that they used this pickup to provide input signal to an off-the-shelf (RPM gauge) tachometer. The same way we use a few turns of wire around a coil HV wire to get signal for OnlineCourse/AlienIgnitionLogging
This could be used as a cam position sensor if the distributor is maintained (but than cam position is not interesting at all). In case
- wasted spark is applied (recommended) the cam position is not needed
- fully sequential ignition (COP) is applied (eg. for IonSense), something (a small HALL or optical sensor) inside the remains of the distributor (where distributor is not used for distributing spark any longer) could be used for cam-sync.
(The ring on ignition wire near to distributor)
The connection to harness:
