Thanks Aqui ! The book from Gilbert was first published in the English as
Gilbert, James. 1975. The world's worst aircraft. Walton-on-Thames [Eng.]: M & J Hobbs in association with Michael Joseph.
The NASM gives in their thesaurus here
as manufacturer for the Bulldogge Siemens-Schuckert, as do Bruno Lange and Gray-Thetford. The first version of the Bulldogge fitted with a radial had on its tail a painted royal (?) designation. Probably this was for Prinz Sigismund von Preussen.
When I have migrated more to my Apple machine I will show more pictures of the Bulldogge, first version.
As probably known the brilliant / enigmatic Villehad Forssman had a very little known career, ranging via Russia to Germany (Siemens and the Forssman Riesenflugzeug 10-engined triplane). Much is not known about his exploits, or at least their is not much information on him readily available.