Today's picture is the bobbin winder, showing the plate that rests against the bobbin while it is being filled. Once the bobbin is full and pressing against the plate it operates the mechanism to disconnect the winder from the wheel. Singer did this with round bobbins, but not with long bobbins.
I hope I'm not boring you all - I could go on for weeks like this. A bit like droning on about a new boyfriend where nobody else can see the attraction...