Yeah, we had one at the shop I worked at.
It's a reflex sight. There is a prism in the base that picks up light and displays the "V", which you see reflected off the front lens, which is "away" from you as it's mounted on the gun.
Considering the era it's really quick. They had a tendency to lose their lens due to recoil and the primitive adhesives of the era.
When you think about it, other than the electric dot it's probably as quick as a C-more. I'd say it's probably worth more to a trap-gun collector than as a useable sight, since 30-40-50 MM red dot sights are everywhere these days.