It's called a "knuckle set" because they efficiently remove the skin from your knuckles? If most of the diesel techs have a set that couldn't be the answer. So what is a "knuckle set" used for?
And I second fatfillup - I'm jealous!
I'm just repeating what he said. When I showed him the pics, there wasn't a hint of surprise in his face, and he instantly recognized the tool. It wasn't like he had to think about it or something.
It isn't just a standard shop either... they've been open since the 40's and specialize in rare engines, and I'm sure they have many tools which have long since been discontinued.