I believe Mike Wenzloff has slots cut in most of his backs these days, but has done some folded backs. (Edit - slots are how Independence tool made their saws and consequently how Lie-Nielsen's are made - and I believe Adria as well). We communicated pretty extensively when he was first starting up and wondering which way he would go with how to manufacture the brass... When he did/does, he has/had a machine shop do the initial bend, IIRC., then either hammers (originally) or presses (he must have a hydraulic press by now) the brass home. He may do his own slitting by now, too...
Leif
www.norsewoodsmith.com