It is a regular wrench, not sure what brand, that has been ground down probably similar to Brad's. I used a dremel and a cutting wheel to cut/shave it away and then cleaned it up with a file. The first bit was hardest but the metal gets a little softer as you cut down into it. It took a few hours but it was a winter project. It slips in between the frame and the engine on the vertical cylinder where a socket wouldn't.
(S4Rs)