What Type of Screw is This?

[Scott J.]

I have a 90 year old house and am removing a large Murphy bed that is attached to the plaster wall. Toward the ceiling, these screws are securing the bed frame to the wall. The head of them is perfectly round, so I can't figure out how to remove them.

Do I just remove them like a nail? They are not threaded.

Just being cautious here because the old plaster will crumble if I get sloppy with the removal.

Thanks!