I only ever knew side-mirrors as "dealer-option" units. As such, they tend to be all over the map as to style, placement and quality.

As an example, my '67 122s has one side-view mirror on the driver's door-frame. It is identical to the two on my dad's Sunbeam Alpine from the same era. I recently saw some very similar on a street rod and asked where they had come from. He gave me a funny look and showed me several styles in a "Custom Rod" catalogue.
These mirrors actually clamp onto the door edge (I happen to like them a lot). You can get them as Iron Crosses too if you trend that way.

--
Mike!