Anyone seen these yokes before?

[mattbrown]

I know they're not high quality but I was wondering if anyone can shed more light on them at all?

 

[Woz]

Had these on a bike I bought and then flipped.

Curious things. From memory the button is used to slightly splay out the brake pads to help wheel removal.

 

[pazaudi]

Coincidentally I came across one of these in amongst my box of bits. It's never been used and I did wonder how it works. I think mine had a diagram or instructions attached to it, I'll have another look later.