Yangdu says the Balance model was created in the HI shop. It is called the "Balance" because you can put the edge slightly foreward of the cho, if I recall correcly, and the khuk will balance on your finger.
The first ones may have been made from files.
Current production Balance models are from spring steel.
I have a Balance model; one of those sold by Bill himself on his father's day of walking West. It is a small khuk, by our standards, but actually does chop a little because of the very slender waist and end heavy design. I've carried mine hiking several times. Nice blade, very lovely, good feel in hand.
munk