Hi I did do some coil setups as per this write up. But to be honest I have re-read it several times this morning and I cant get my brain on the right wavelength!!! It did work effectively as I recall as originally I could not get the coil to track in by trial and error adjustment. National must have had a systematic approach but would not be dealing with coils designed and tracked for one model being used on another as many of us are. Lucky is the person with matching serial numbers!!
There is also a link in the thread from Andrew giving more of the maths behind these coils.
https://www.vintage-radio.net/forum/...d.php?t=111382
Pete