Owen wrote:
"Not to imply that Efficiency = Q."

It does.

Q = energy stored per cycle / energy lost per cycle. Q = XsubL / R

Efficiency = output / input.

Output is the energy given back by the coil when its field collapses.

Input is the energy required to charge the inductor`s field plus the
energy required to supply the losses.

Net output is equivalent to coil reactance and net input is equivalent
to the effective series resistance loss. Therefo Q = Efficiency.

Best regards, Richard Harrison, KB5WZI