The hole at the end is not sharp.
The circular piece in the middle does not move.
Only the end holding the handle moves, which seems just to be a
condition of age and dry wood (loose fit).

Brad nail set? Interesting. I've never seen one, at least not like
this one. The hole on the end can certainly fit brads and small nails
w/o large heads. I'm not sure what he would have used it for. I see no
evidence of it anywhere in the shed, garage or house. Was it for use
on soft wood? It doesn't look as if it has ever been hammered.

I took another photo of it, zooming in on the working part. I tried to
take a shot of the end hole but it comes out too blurry.

Maybe photo 2 can help nail down it's identity.