that is a great , informative post Gerry.
The grid dip meter is also interesting. I have never used one. It picks up on the resonant frequency of a tuned circut right? Do you feed the transvormer via a signal generator, and by varying the frequency a bit , see where the meter peaks? I am guessing, am I close? the frequency is a product of a given inductance and capacitance, so you are testing using the grid dip meter to see if the caps you used are the right size to make it oscillate at 455 Khz right?