Twin lens reflex, this is a very solid and versatile camera. Maybe too much solid and heavy. But this is a good compromise considering you have 6x6 negatives with interchangeable good quality lenses. I bought this one to do professional work as many photographers with low budgets still do. For action pictures there is a porrofinder that you mount over the ground glass and have an instant left-right corrected image. It is like a monoreflex with 2 kg: almost convenient. For still life work there is a parallax corrector mounted over a tripod that (once you have framed the subject) allows you to lift the camera in a way that the taking lens will come exactly to the previous position of the viewing lens. It has also a needle that slides down under the ground glass as you focus closer. That shows you the actual top of your picture. That is the fast way to avoid parallax error. Of course you can't see then the bottom of you picture by the same amount. It has also a bellows that extends enormously for close-ups. It is really a performing instrument but design... if it was not from Japan I would say it is a sovietic project.

Mamiya started with the concept in the late fifties. I didn't find exactly but this C330 might be from the following decade.
To see more about the Mamiya TLR system try:   Patterson;