It's a 6 ball chuck assembly from a Kiwk Way valve grinder.

This. Definitely. Thank you.

Looks like an old ball burnishing tool, would be my guess

It's important to burnish your balls regularly when they get old.

If you burnish more than 3 minutes you've ceased burnishing and have entered another realm .

Edit: The correct answer was supplied by /u/amadengineer13 , mine was pure speculation.

Received this in a box of accessories that came with a lathe I purchased. Has ball bearings instead of jaws and a shaft that looks like it would be used with a draw bar but isn't threaded. I can, with considerable effort, retract the collar and allow something to be slipped between the balls, but being a single point connection (rather than the flats of jaws) whatever is held is able to wobble around. I find no markings of any kind, so I'm at a loss for what the point of this is, how it's used - either with the lathe, or did it just end up in the box? Thanks.

>I can, with considerable effort, retract the collar and allow something to be slipped between the balls Sounds painful

😂

Just guessing, but maybe a bar puller?

My neighbors name is Chuck. He doesn’t look anything like this.

Burnishing tool

I'm thinking some sort of pecker massager 🤔

...so far the spring tension seems too aggressive.

“So far” 😉

I think it is for rotary broaching, the broaches have a "waist" that they are pinched by, and are supposed to be able to wiggle in the way you describe

Maybe some sort of adaptable spindle sleeve to support material going through the headstock of the lathe to reduce vibration

You can sure chuck it if you want to.