meeni wrote:
has a smoked finish so you cannot see it when the car is off, ive never heard of two coil wires from the tacho, could be the case

My smiths tacho had two wires for the signal they were white wires joined by a bullet connector that came straight from the ignition (ie the key start)
You might be able to tell which ones are the signal because they(one of themanway) gets wrapped around a doughnut type thing(on mine but I immagine mine is a fair bit older than yours) in there which picks up the electrical pulses from the dizzy.