nothing at all, really... but I just tried it on my machine and scroll lock comes up as keycode 78 (Model M through Belkin converter, just fired up xev and hit the scroll lock key, if that makes any difference)
KeyPress event, serial 33, synthetic NO, window 0x5200001,
root 0xa1, subw 0x0, time 4878851, (319,159), root:(337,290),
state 0x10, keycode 78 (keysym 0xff14, Scroll_Lock), same_screen YES,
XLookupString gives 0 bytes:
XmbLookupString gives 0 bytes:
XFilterEvent returns: False
KeyRelease event, serial 33, synthetic NO, window 0x5200001,
root 0xa1, subw 0x0, time 4879011, (319,159), root:(337,290),
state 0x10, keycode 78 (keysym 0xff14, Scroll_Lock), same_screen YES,
XLookupString gives 0 bytes:
XFilterEvent returns: False