Does anyone know

TrailBeast said
Looks pretty darn big for a screw extractor, but I have seen those with that same design.
In the pic I get the impression and it's about 3/8 or so on the shaft?

1/4"

Abodybomber said
I was thinking valve guide reamer,with a stop for valve guide length.

That sleeve moves free and no way to secure it. Looks to me like it's just used to put a wrench on it to turn it

TrailBeast said
It also just occured to me that reamers usually cut turning clockwise, and an extractor would tend to cut counterclockwise.
Which is it?

It's designed to cut counter clockwise