Joel Kolstad wrote:
"An Interesting result of the above is that the polarity of the voltage
coming out of a shielded loop should be opposite that of what`s coming
out of an unshielded loop."

Yes, a phase reversal is produced by the change of current direction
between the outside and inside surfaces of the loop shield. But carry
your logic a bit further. There is a second phase reversal provided by
the inductive coupling between the inner surface of the loop shield and
the wire loop inside the shield.

The wire loop is the secondary of a transformer. Induced and counter emf
are 180-degrees out of phase with the primary or source emf. For
graphics see Fig. 5-14 on page 79 of Robert l. Shrader`s "Electronic
Communication".

Best regards, Richard Harrison, KB5WZI