EDIT: I think I figured this out actually... would it make sense that the NTSC models have 3 and 4 as the switch positions (to equate to channel 3 and 4 in the US) and the PAL models have the L and H instead?
Dumb question... is there a way to tell if an A520 is PAL or NTSC other than hooking it up and seeing what you get? Come to think of it, how do you tell which default an Amiga is?