This design is intended to allow a CB radio or other similar mobile radio to be mounted to a desk or shelf surface, either above or below the surface the mount is attached to. Either way it leaves the speaker, which is usually on the bottom of the radio, free to be heard rather than flat against the desk or having to leave the radio upside down on the desk to hear it.
I recommend a .2mm print height to ensure correct functioning of the threaded bold/clamp interface.
The author hasn't provided the model origin yet.