Kodak made Duaflex cameras from 1947-1960 with this one here being the last and best looking model. The IV has the nice feature of having to turn the knob before you can press the shutter which will prevent accidental double exposures - but it has a switch to over-ride that feature too(which you will see below I used). Besides that the only other control is the shutter speed - 1/50 or "bulb" (or "time"/"Int." as labeled). Kodak did make slightly nicer(and rarer) versions of these cameras with some focus and aperture controls.
'Laura and Rotaynah' - I like how the farther corners start to blur - it gives a dreamy look to the photos.
"Barn Door" - on Kodak T-Max 100 developed in HC-110(b)
I used the "over-ride" lever to make this double exposure of Laura.
Dave and Eva
Another double exposure.