Picked this up last night, belonged to the grandfather of someone on Gumtree:
Certo Dolly Super Sport 1937 by
John Rodriguez, on Flickr
At first sight it's an old 120 folder, a Certo Dolly Super Sport, made in Germany in 1937. It is however fairly advanced for its time and quite heavy on features. Carl Zeiss Jena 75mm Tessar, uncoated due to its vintage. Compur Rapid shutter going up to 1/400th (with a very heavy second spring). Helical unit focus with coupled rangefinder, separate viewfinder with adjustable masks. Dual format 645 or 6x6 via film plane masks, also removable back for glass plates, and removable lens for use in an enlarge, microscope etc. Red windows under a flap on the back (which doubles as a notepad), but for 6x6 there is also a rudimentary counter on the dial of the supply spool (which can also be wound backwards, not seen that before). It's already got a film in, just one shot taken, so will finish it off and see how it looks. Tenner! Also came with a Kodak Brownie Popular box camera.