I have two, identical 4″ 3-jaw Burnerd chucks.
One that came with the ML7 that was dug, rotting, out of someone’s garden shed (but cleaned up not half badly) had only outside jaws.
The other I just picked up on slightly incomplete Myford dividing attachment. The chuck appears new although with some slight surface rust and has inside jaws only.
So … are the jaws matched to their specific chuck or can they be swapped between chucks?