This is an image of the other side of the Rollei showing film advance crank and frame counter. The Serial No is situated under the bottom lens, mine is T2194937 from which I have found out is the T2 made around the mid sixties. I am certainly not an expert on Rollei's, the controls for the speed and aperture are not between the lenses on this model, but on the right hand side of the lower lens, looking at the front of the camera.(Best seen on other image) Pulling the lever out adjusts the aperture, then withe the lever in normal position this adjusts aperture and speed together to alter dof.