I own 4 Barrages now, a 580-1102, a 581, a 586-1401, and a 585 custom shop in D2 blade.
All are excellent knives, especially the 586 and 581 with their near-FFG M390 blades. They are all a little thicker in the hand than the typical BMK, but this is a function of the assisted open (need room for the coil spring).
Personally, I enjoy the extra heft of the 581/6 (due the G10 scales), gives the knife a much more solid feel.
As for the fleabay example of the 581, the black thumbstud on a satin blade is not a bad thing. My example also has a black stud.
While this combo is rare, it is not unheard of. My knife also has a more glossier black clip than the typical 581, more like the old 930 which appeared more like a black chrome than a painted or plated finish.
However, the 'course' stone washing of the fleabay knife would have me very concerned. I have
never seen a true BMK with a stone wash that aggressive (Other than a Ritter Griptillian). My opinion is that either the photo has been editted or the knife has been modified. Either way, 237 Euro is WAY too expensive for a new 581 IMHO.