Here is one of our coil winding machines winding the secondary for our EL transformers but the same thing applies to wind other coils such as these Hankins:



https://youtu.be/791MhDiOLiA

After the termination of the leads and adding the diode we confirm the inductance of the coil both static (with NO iron plunger inside) and active (WITH the iron plunger inside).

You can see how much it changes between the two states and this is the most accurate test to confirm the coil has been wound correctly.