Duane Watts Swivel Knives, Looking for information

[IH460]

Checking out some Duane Watts knives online and can't seem to wrap my mind around how the blade/yoke is held in the bearing side. I see that they are interchangeable, offering the option to swivel the blade, or swivel the yoke like a traditional knife. When swiveling knife, I am understanding the yoke is sleeved into the body and secured with set screw to hold it stationary. I see there is a bearing pressed into the body on the other end, and a hole that appears to be for a set screw, but see only brass inside hole. Is the blade/yoke only held in by friction to the bearing or is there a retention ring, etc. that secure it?