It's an outdated bullet feeder which is attached to any Star loader at the seating station.
The image that you are showing is incomplete to be a functional add-on.
I have the complete unit but they take different part(s) to load anything other than 38 spl. caliber.
If you wish to research this unit more than this another member placed a .pdf
file from the business that made this add-on which is to large to attach to this reply.
I will PM you for an email address to send it to you.
