Quote Originally Posted by Gerald Koch
Mamiya made a porroprism for the C3 and C2 families. So you can have your choice of either waist level or eye level viewing. There is also a choice of lenses, wide angle to telephoto, and a sheet film back.
You may also be able to use the pentaprism that Mamiya made - it works on my C330 and C220, but I am unsure if it fits the earlier cameras.

It is brighter then the porrofinder (which used a mirror), and the image is not reversed, but it is heavy, and can be expensive.

I used to use it for weddings - it permits you to avoid the dreaded "navel eye" view of the world