You have to measure the ohms resistance between all the pins. Open up the control box and figure the circuit.
I presume your thinking of building a coil for it.
I mentioned in another forum, its not that easy, there's science and a bit of witchery behind building them. Otherwise everyone would be making them.
Coil building info can be found on the Geotech Forums, specific sub forum. It may take you 10 coil builds to get one that will work properly, maybe. The cost factor will be more than buying one. Upwards towards $500 or more. Plus a whole lot of man hours, maybe months. Plus the frustration.... Be more economical to wait for DeepTech to get there's finished.
Mono coils for Pulse Induction metal detectors is pretty easy and straight forward. DD, Concentric etc. type coils are not!!
https://www.google.com/search?q=metal+detector+coil+winding&newwindow=1&source=lnms&tbm=isch&sa=X&ved=0ahUKEwjurruyo8fjAhUHTawKHeDLDkEQ_AUIESgB&biw=1760&bih=833
By the way, the thought crossed my mind
to build my own accessory coil for the X in a smaller size to suit my needs. Not that desperate at this point. I can build some pretty mean mono coils for PI's, probably built 50 but, DD's and concentric and the dynamics behind them would be a challenge. Made one attempt to build a small DD coil for the Tek Omega I had about 6 years ago with some input from Dave Johnson (First Texas). It actually worked, just not stable and target ID's were all over the place. Trashed it.