Long-stalk racing Mirrors

I noticed on certain cars at the Goodwood Revival there were rectangular mirrors on long stalk/arms mounted to the door's window frame. Does anyone have better photos or a detailed description of how these mirrors were attached? The blind spot on the right behind the passenger door is of concern to me, and even a round convex mirror (2 1/2 inch) doesn't seem to be enough when you are on the freeway or turnpike.

I noticed that the car in a video had vertically-oriented mirror, and a second, horizontal, convex mirror, as in this photo":


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