The "mechanism" that locks the swivel base and rotation of the Yost rotator vises is just a large through bolt to which the lever is threaded onto.
Here are some pics of a 4 1/2" Yost swivel jaw rotator I acquired last year. You can see that the "barrel" that slips over the swivel base and accepts the static jaw (nothing is really "static on this vise") is partially cut down the middle and it's essentially just pinched when that bolt is tightened.
Great photos thanks for the informative post.








