What’s that headband with a round piece of shiny metal attached used for?
Cecil himself answered that question way back in 1993.
A mirror to illuminate dark areas (!)
From the days before LED headlamps 
Ah, so he did! Thanks.
When I did two weeks of ENT back in med school, they gave me one of those to use for the rotation. It was cool, but it’s no substitute for an actual light.
We called 'em “head mirrors”.