I read a post asking this question, but there is no answer for actually removing the box. I do want to remove the box to install a retrofit recessed LED light. My bungalow was built in 1952. All ceiling light box has this stud and nut anchor. There is also one on a vertical wall, so the stud is not necessarily for load bearing. Please advise me on the construction of this box, and how to remove it.
These hangers were typically used in ceilings where they wanted the light to be somewhere which required space or location between joists. The bracket is typically nailed to both opposing studs or usually under the plaster or drywall.
You could cut it with a hacksaw and move it out of the way. Or for more work, cut a separate hole for the recessed light and then patch the old hole from behind.
You mentioned "retrofit". Retrofit usually means a prior recessed light fixture, which this is not.
I figured it out. It is the plaster around the edge of the box that is preventing it to come out. Once I removed the nut and chiseled away the plaster around the box, it came out readily. I then had to saw off the 1/8" hang bar.