As far as i can remember its not 501 and 502. Its 507 and 502. Yes these are hard to find compilations which boasts excellent artists (Siakol, Kelts Cross, Inquisition, Sugar Hiccup, Feet Like Fins, Shimata Colony, Skrewheads, Goo, Dominion, Iconoclast, Fearless Freep, etc....). Why O7 and O2 if you have the cd its the catalog number of the album . Yup, no kidding (for 507 : ANR- CD-97-507, for Immaculate 's Too Good To Be True: ANR - CD- 95-503). Get It?
So what's Alphanumeric 501? Its Color It Red's Hand Painted Sky (Debut Album) Serial Number ANR - CD-95-501. =)