Mark Bulgier wrote it pretty well.
When I was faced with a obscure headset, and no reference, I knocked off the crown race, turned the frame upside down, placed three candidate balls about 120 degrees apart in heavy grease, set the crown race in position, and looked to see it it passed the looks right test. If it did, I assembled the whole thing. I have either been lucky or this works well.
John Jorgensen
Torrance Ca USA