Someone probably didn't know what to do with it so set it out for the trashman. Machines used to be made of metal so it would be heavy, which can be an advantage when it comes to sewing for long periods of time and on thicker fabrics.
Give it a cleaning yourself and oil it and then use it. You will figure out how to get the bobbin out, tip it to the back so you can see the underside and then go at it. It has to come out and you will find the solution to the bobbin case. Maybe someone will come up with a manual you can copy.
Carol J.