The Kodak Duo Six-20 is one of the first three models to roll off the Nagel Camerwerks factory line not long after it was purchased by Kodak in 1932.
In researching this camera, I read that cameras intended for the U.S. market are branded Kodak, while those sold in Europe carried the Nagel logo. However, I'm not in total agreement with that, as I have cameras marked Kodak and the lenses are marked in meters, which would have been for the non-U.S. market.
Think of the Duo Six-20 as the big brother to the diminutive Kodak Nagel Vollenda. This is a 6x4.5 roll-film camera that gives you 16 shots on 620 film. For those who don't know, 620 film is essentially 120 film on a thinner spool. You must respool 120 film onto a 620 spool if you plan to use this camera. Once you get the hang of it, repooling takes only a couple of minutes.
The Duo Six-20 is a zone-focus camera, although later models had a coupled rangefinder. My camera has the less commonly seen uncoated Carl Zeiss Jena Tessar lens in a Compur shutter, although many had the Kodak Anastigmat, of which some possibly are rebadged Schneider-Kreuznach Xenar. Both are excellent lenses.
There is no flash synchronization, so it's best to use it in the daytime.
This camera really folds flat, and could probably fit into your pocket, except for the weight, which is significant.