Thank for your advice.
The problem are probably the fotos I made. The colour is not grey it´s a light blue. Jacket has no solid pattern, it´s what we call in german "Pfauenauge" which means "peacock butterfly". I don´t know if that the right name in english. Here is a foto from the pattern and colour:Warning: Spoiler! (Click to show)
So thats why I think it´s a odd jacket and I react a little bit astonished when you call it "orphaned suit jacket".
Honestly, it still looks a bit suit-ish to me. Kinda reminds me of birdseye, which is a suiting weave/pattern. I think being light blue moves it a bit away from orphaned suit coat territory, but maybe you would need casual details like patch pockets for the full effect.