According to phaq, if you have a Sun 13W3 to VGA adapter but an SGI machine, you break off pins 1, 2, 4, 5, 6 and 7. Or you could just break off 10. Of course, you can’t use this on a Sun after you’ve modded it, but I heard that if you just break off 10, you can actually get it to work with both Sun and SGI.
As a side note, I cannot believe I just announced that I have an SGI Indy and nobody seems to freaking care.