Ralph Mowery wrote, on Thu, 19 Feb 2015 17:49:33 -0500:

I wonder if the Husqvarna people use somethink like that

This is most likely the shape of the tool used to spin
the brake release wheel!

1. https://c4.staticflickr.com/8/7439/1...604227cf_b.jpg
2. https://c4.staticflickr.com/8/7391/1...6d987d3c_b.jpg
3. https://c1.staticflickr.com/9/8677/1...921a12ae_b.jpg

Those are screenshots from this video:
https://www.youtube.com/watch?featur...DBdq0Y#t=25 5

What the guy did was sacrifice a hole saw, by notching it
to fit the chain brake spoke wheel.

That seems to be the easiest method of all.