The Kodak Duaflex is a 620 roll film pseudo TLR made by Kodak in the US, Canada, and UK. The original versions were available from December 1947 – September 1950 in the US, and 1949-1955 in the UK; the Duaflex IV was finally discontinued in the US in March 1960.
The various Duaflexes had Bakelite bodies (identified by Kodak as “Kodadur”) with metal fittings and trim, and were available with either a simple fixed focus 75mm f/15 Kodet lens, or with a 72mm f/8 Kodar triplet lens in a front-element focusing (to 3.5 ft.) mount. The Kodar lens had Waterhouse stops of f/8, 11, and 16. The shutter had speeds of “I” and “B”, and was synched for use with a Kodalite Flasholder. Early U.S.-made models (Duaflex and Duaflex II) had a dedicated Duaflex Flasholder, which was synchronized for SM and SF bulbs when the camera was set on “I”. No. 5 and No. 25 bulbs could be used, but the “B” setting was required for those types. Later models (Duaflex III and IV) were modified to accept the aforementioned Kodalite Flasholder, which was also used on the Brownie Hawkeye Flash Model and other Kodak models.
A special feature of the Duaflex line was double-exposure prevention, meaning the advance knob had to be turned to the next exposure before the shutter could be activated. This feature could be overridden by pushing the little lever below the shutter button.
~Description courtesy of Camerapedia.fandom.com