Your stove is the World War One version of the German Heater I posted pictures of above. If you look, your stove is identical to the first picture up there. Unless you have them somewhere, your stove is missing the side wings that go on either side of the loading door. These side wings are in place to create convective turbulence around the stove to improve the distribution of heat.
These stoves are of exceptionally high quality and of an excellent scientific design. They are very efficient. This stove should be in someone's house burning coal as it was meant to do.
In its present condition I wouldn't expect to get more than a few hundred dollars for it. Totally restored in like new, useable condition these run around $2,000-$2,500 dollars. Again that is if they are perfectly restored to brand new condition.