Brainstormin..............

Hmmmmmm.........certainly, the possibility exists, but how do you explain the 12V at the coil ..............?

The module should trigger to sink the coil to ground ............

(scratch head here and go off to investigate)

Do you have 12V at the coil -while cranking-?

I do believe so...........but not verified by me personally.

Unfortunately, was not able to visit with car today, and will have to pick it up later......(not mine)

If you're getting a spark when you turn the ignition switch to off, the coil must be getting a ground. Turning the ignition switch to off and removing the 12VDC from the coil causes the electrical field in the coil to collapse causing the single spark. Normally the 12VDC remains on the coil and the ground circuit opens and closes causing the same effect. So most likely cause will either be:
1. Like Steves280 suggests - no power to coil while switch is in the start position.
2. constant ground to coil - Since you already replaced the ignition module a faulty ignition pickup in distributor is most likely.

Well, I am 100% sure my problem was the ignition switch and I had the same problem with the same "only spark when turning off" symptom

<http://www.zcar.com/forums/read.php?f=1&i=494308&t=494308>

Hmmmmm.........

...........only piece of the puzzle not already checked / replaced.

Owner was going to ..........errr.......pick up a pick up.

No visible damage and/or wiring problems to existing, and no - hard numbers - to compare to as far as resistance, etc., are concerned.

Yup.............

......do now, verified at coil terminal while cranking.