Yes, 35 cine format. There were viewfinder cine-cameras, actually in the past they had been the majority. But in this case not a viewfinder camera in the actual meaning. I have to correct myself on that.
Kubrick used a camera where he could employ the lens alternatively, though clumsy, for taking and viewing. So he could focus via that lens.

Nevertheless for that 0.7 lens the omission of the reflex system and the making of a proprietory lens mount was not sufficient. Further re-building of the camera was necessary.