The Bobbin holder is held in place by 3x9x9mm magnets. The pockets are for holding sewing needles in place by magnetic magic.
The old hard plastic part broke because the sewing machine was put in storage with the bobbin holder engaged. In this magnetic design, this is prevented as the bobbin holder is simply going to clip off in case of external force.
It is a fully functional repair and is used regularly.
The author marked this model as their own original creation.