Brass

Today I found a bronze something.
Never seen and I absolutely do not know where the need or use for.
Thought it has something to do with the derailleur of a bike but can not place it on the bike. I have images of a derailleur viewed in Google but it is not listed. So it must be something else.
It is not a pen holder on the desk.
You can remove the large plate of the reel with a small screw gain.
So a mystery to me.