Sadly I don't know exactly what they are.
I have several and they are all way bigger than any
fibula knobs.
I think they are a form of furniture decoration - and by furniture I mean the archaeological term which includes what we think of as furniture, plus chests, boxes, door fittings, etc.
Don't know if these were meant to be pulled or are just decorative knobs, stud ends, etc.
Shawn