The scans are labeled M-S, but you're right: I'm not 100% sure (and actually, mangaupdates has "Froger" listed as the group that released Volume 3).
In the end, the scans were well translated, so the little issues with color,etc. were easily forgotten.
Another tip (to avoid having to manually edit the levels on such scans), is to use an app like CDisplay that has built in gamma/color correction. The default color correction along with a gamma correction of about 0.70 should make these scans turn out pretty good (or, at the very least, more black).