You could start by giving the protrusion at the bottom a whack with a hammer. I don't see a screwhead or hexagonal nut at the bottom, so it's most likely a smooth pen with the head resting on top.

If it doesn't immediately give way, proceed with paint removal to uncover more details.

You could start by giving the protrusion at the bottom a whack with a hammer. I don't see a screwhead or hexagonal nut at the bottom, so it's most likely a smooth pin with the head resting on top.

If it doesn't immediately give way, proceed with paint removal to uncover more details.