I don't mean to shit on your parade, but the frame not being a Soul, and a more niche SS frame, I wouldn't base it on Soul prices. The two Souls on ebay are £155 and one £185. Even though yours has a detachable mech hanger, I'm sure if somebody specifically wants gears, they'd probably rather a...
From their site:
Mk1 was 1997-2000, mk2 was 2000-2003.
"1997 to Early-1998 Frames have a 26.8mm seatpost diameter - Mid-1998-on Frames have a 27.2mm"
Otherwise, the frames look identical, neither had disc mounts but the mk2 had a disc brake adaptor.