First off Mike, thanks for your interest in this. You may be correct as to how the strobe is triggered, although I don't think that you are. If an inductor were involved the strobe timing would retard as the speed of the machine increased due to the fixed lag time to ramp up the coil. I think the falling voltage triggers a tube amplifier circuit. The plate of the tube drives the strobe (I presume).
A model T timer is a rotary switch driven off of the camshaft at half engine speed. Instead of producing a spark when the connection is broken, it completes a circuit to a relay. When the points on the relay open the field collapses and the spark occurs. On the Model T there is no battery involved in normal operation, the current is supplied by an internal permanent magnet AC generator (alternator) that is indexed to the crankshaft. The timer actually acts as a mechanical rectifier (commutator) and picks off a half cycle of the AC potential. The coil then fires when the current rises to a preset level (about 3 amps typically). Because the coil fires at this preset level, the coil will usually fire at the same point on the AC waveform regardless of speed, thus keeping the timing steady as the engine speed increases.
All of this has nothing to do with the problem at hand. I want to test the accuracy of these timers on my old fashioned distributor tester. I want to spin the things up and see four arrows 90 degrees apart, just as I do with a four cylinder distributor.