Well, Dave is obviously right with the
Siemens-Schuckert Forsman Giant or R-type that did not got a roman numbering. But he missed rule #8.
I haven't seen a rear-view so far, but this clumsy fuselage and the 4 four tractor engines are a clear hint, including the (occupied) gunner pulpit.
But the plane here is not in the layout Villehad Henrik Forssman had initially designed it. The early wing structure proved to be too weak and 6 additional struts had to placed either side. Then Forssman redesigned the wings and cause the plane was exceptional tail-heavy he added a gunner gondola at the front which one can make out at the front, where a fellow is looking over the rim. Also the engines got a streamlined covering that they did not had before. Just the plane (maybe thankfully
) did not fly - mainly because the engine power was too weak and Forssman lost his job with Siemens.
Later with Harold Wolff and the Steffen Brothers further changes were made including more powerful engines installed and the aircraft finally flew. I believe only twice. After it passed it's acceptance test the wings broke into pieces while the engines were test-running on the ground...
Does someone know if it ever got an official registration since it was purchased by the army? 
Cheers
Aquilius