Well, in case anyone cares. I developed this roll, based on my thinking that there was some evidence that it had been run through a camera
(due to the bend marks at the leading end of the backing paper) and may have been exposed.
Stupid me, I thought there might have been some older camera that would require you to re-roll the film back unto the original spool once the film had been exposed.
Turns out that Sirius Glass was correct. About the last foot of the backing paper changes color from all yellow to yellow with a red border, and about the last 6" is all red with a black border and says "EXPOSED do not re use".
Anyway, the film was clear with just a few smudges of light leak at the edges, no frame lines anywhere.
So, I deserve to be hanged, I wasted a good roll of a classic film which can't be replaced.