I have a Kundo from around 1950 that looks similar to yours, at least the movement. Mine is spring driven with the mainspring located where the gear sticks out from the side. I also concur that you are missing the balance at least, and likely the entire spring assembly. You should have a large slotted screw head at the top of the cylindrical cover on the back. This should be attached to a wire and a balance at the other end (the thing with the balls you see in examples online). Again, I am describing the manual wind version.
I bought the Horolovar 400-Day Clock Repair Guide https://www.amazon.com/Horolovar-400-Day-Clock-Repair-Guide/dp/9992387262 that describes a great number of varieties as well as what springs to use (the wire I mentioned) and how to set up the spring as well as general repair guidance. I don't remember much about battery driven models though I wasn't interested in them so I may have overlooked it.
Oh, as far as value, they don't carry much as they were mass produced for much of the 20th century, particularly after German industry got back on its feet after WWII. Many many were purchased by servicemen overseas during the cold war. I suspect my dad bought the one I have while a soldier.
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