you know what that spit pilot uses the mirror for?
Mostly to check control surfaces on the tail being there and working properly.
The myth that you couldn't see anything in the mirror is kind of old. If it were true, why would so many aircraft come from the factory with mirrors attached> So the pilot could so makeup?
You only needed the mirror to get a flash or a glimps of another aircraft behind, not so you could read his tail markings.