Lets play "What the hell is this and where does it go?"

Undoing the speedo cluster on my decrepit 1981 R100RS and fiddling with cables etc, this little dodad fell to the ground.  My first action was to frown and say "HUH?" in Sanskrit.  Any takers on what this is, what it does and where does it go?
Had the little wedge from the left handle bar fall off, only to find it again and not know where it goes.  Tagged and bagged it though.  Will look on relevant sites where it goes. 
This is turning out to be challenging.........