Z5TF – 12127 – C is a Mk I distributor – this is the later style distributor – there should also be a date code stamped into the aluminum.
The 1st engine group I have a listing for this distributor is the F21KA engine group. It could have been introduced earlier; I just don’t have a record of that yet.
C4OF-12127-A is the early style distributor with an oil port.
C5AF-12127-M is the MK II distributor.