After looking more closely at the Favorit and doing some minor cleaning and adjustment (thrusting typebars must be perfectly straight or they can get stuck), I noticed a few things. I've used it for typing for a few things already, and it is a German keyboard, but it has some oddities. First, I realise now it is also intended to type French. It has an acute accent with an e (é) and a dead key which types a grave accent and circumflex. And of course it has A, O, and U with an umlaut. However, it does not have a cedilla or a way to type a diaeresis (umlaut) over an i or e. The comma seems to be able to fit for a cedilla. Maybe these symbols were used in German at the time for something. I do not know. It is perfectly suited for writing German. It lacks and apostrophe, which makes is not fully suitable for English (especially for my name..."J. F. O'Neill"), and it is partially good for French.
Here is a video with the top off (top comes off after loosening some screws, it is not something which is intended to be opened often). It works surprisingly simply. There are only three parts (including the actual typebar, the key lever, and the part in between). There is no sound in the video, but it sounds mostly like a regular typewriter.