I see the Dornier Do 11 is a perennial favourite of this thread - which is a bit odd for such a weird, slow and clumsy aircraft…
What gets me every time is the fact they designed it with retractable undercarriage, but once retracted it was nearly impossible to deploy again, so most of the time, the planes just flew with their gear locked in landing position…
By the looks of it, that is an example in Bulgarian Air Force markings used between 1938-41.