I'm guessing it was either a raw binary dump, or the old (even then obsolete) IFF PLBM format, which preceded the well-known IFF ILBM format. PLBM files were fo

I'm guessing it was either a raw binary dump, or the old (even then obsolete) IFF PLBM format, which preceded the well-known IFF ILBM format. PLBM files were found on the famous EA Kaleidoscope demo disk.