They are not all that rare, I have one myself. It certainly couldn't be the only one to exist.
The rear SWL was caused by die polishing so there would be as many struck as to when the
die was polished and when the die was retired.

Welcome to the forum.

Can you supply a picture of what you think is doubling on your Terry Fox dollar.

What Bill said plus that is Machine Doubling that you see, a worthless type of doubling.

Don’t agree, that is a A between denticle

Welcome to the Forum
First, a German planchet is not an error, there were 10 million produced in Germany to help with the
production during the introduction of the Toonie in 1996.
That extra string of “beads” you see is just damage

Not an error, that is the way they all are. Just check others 1/2 penny bank tokens and compare.

It has taken a hit distorting and flattening the letters and number.
Just a damaged coin.

Could you supply a picture, there are a couple of things it could be but would have to see it first.

There were also 10 million of the O/D prefix printed.
Is it certified UNC or is this your own assessment?

What Bill said.
Have seen this quit a few times where the core has been deliberately rotated.
It is impossible for this to happen at the mint as the ring and the core are both struck from a single die.

Good work Bill,
glad we have an expert in Vickie’s, I would never have caught that.

Value always depends on condition and prefix. You have not provided either one.

Hard to evaluate without a picture of both sides. All I can tell you is that there were 10 million
with the prefix A/T printed, the maximum for any series.

Compare it to other 1979 dimes, I think you will see that this normal.
Certainly not an error in any way.

Not disagreeing with anything you say CanuckCoinGirl, but until you can get Catalogues, Dealers, Grading companies etc. to stop using the term, I think it will be with us a long time as it is embedded into our little
coin collecting minds.